diff --git a/docs/API.md b/docs/API.md
index b15b815..4c40894 100644
--- a/docs/API.md
+++ b/docs/API.md
@@ -653,11 +653,12 @@ the server has `GOOGLE_BOOKS_API_KEY`, then Amazon's "Print length" via SearchAP
 
 #### PUT /api/v1/documents/{document}/info
 
-Manual fixes when the lookup got it wrong: `{"cover_url": "https://...", "page_count": 433}` (either
-field optional). Manual values stick, since lookups only fill blanks; `null` clears a field so it's
-looked up again. `language` (a BCP 47 tag) can be set the same way and then stays over device
-syncs; `null` clears it so the next device sync fills it again. Returns the stored
-`{document, cover_url, page_count, title, author, language}`.
+Manual fixes when the lookup got it wrong: `{"cover_url": "https://...", "page_count": 433,
+"genres": ["Fantasy", "Heist"]}` (every field optional). Manual values stick, since lookups only fill
+blanks and Hardcover's lookup leaves manual genres alone; `null` clears a field so it's looked up
+again. `genres` takes up to 10 names of at most 64 characters. `language` (a BCP 47 tag) can be set
+the same way and then stays over device syncs; `null` clears it so the next device sync fills it
+again. Returns the stored `{document, cover_url, page_count, title, author, language, genres}`.
 
 #### GET /api/v1/documents/{document}/cover/candidates?q=
 
diff --git a/migrations/0033_manual_genres.sql b/migrations/0033_manual_genres.sql
new file mode 100644
index 0000000..e706fcb
--- /dev/null
+++ b/migrations/0033_manual_genres.sql
@@ -0,0 +1,2 @@
+-- Genres set through PUT /api/v1/documents/:document/info stick over Hardcover lookups.
+ALTER TABLE documents ADD COLUMN genres_manual INTEGER NOT NULL DEFAULT 0;
diff --git a/src/models/cover.ts b/src/models/cover.ts
index 51072b5..9a29bbf 100644
--- a/src/models/cover.ts
+++ b/src/models/cover.ts
@@ -215,11 +215,11 @@ async function sharedBookInfo(
   return info;
 }
 
-/** Store Hardcover's details on a document (a miss just records the check). */
+/** Store Hardcover's details on a document (a miss just records the check). Genres set by hand stay. */
 function saveHardcover(db: DB, userId: number, document: string, hc: HardcoverBook | null): void {
   const json = (v: string[] | undefined) => (v?.length ? JSON.stringify(v) : null);
   db.prepare(
-    `UPDATE documents SET hc_id = ?, hc_slug = ?, moods = ?, genres = ?, content_warnings = ?, rating = ?,
+    `UPDATE documents SET hc_id = ?, hc_slug = ?, moods = ?, genres = CASE WHEN genres_manual THEN genres ELSE ? END, content_warnings = ?, rating = ?,
        series = ?, hc_series_id = ?, series_position = ?, release_year = ?, description = ?, hc_checked_at = ?
      WHERE user_id = ? AND document = ?`
   ).run(
diff --git a/src/models/merge.ts b/src/models/merge.ts
index 5116e83..048de77 100644
--- a/src/models/merge.ts
+++ b/src/models/merge.ts
@@ -148,8 +148,8 @@ export function mergeDocuments(
 
     // documents: canonical metadata wins, alias fills the gaps.
     db.prepare(
-      `INSERT INTO documents (user_id, document, title, author, filename, filesize, status, status_at, pause_reason, start_date, finished_date, cover_url, page_count, language, updated_at)
-       SELECT user_id, ?, title, author, filename, filesize, status, status_at, pause_reason, start_date, finished_date, cover_url, page_count, language, ? FROM documents WHERE user_id = ? AND document = ?
+      `INSERT INTO documents (user_id, document, title, author, filename, filesize, status, status_at, pause_reason, start_date, finished_date, cover_url, page_count, language, genres, genres_manual, updated_at)
+       SELECT user_id, ?, title, author, filename, filesize, status, status_at, pause_reason, start_date, finished_date, cover_url, page_count, language, genres, genres_manual, ? FROM documents WHERE user_id = ? AND document = ?
        ON CONFLICT(user_id, document) DO UPDATE SET
          title = COALESCE(documents.title, excluded.title),
          author = COALESCE(documents.author, excluded.author),
@@ -163,6 +163,10 @@ export function mergeDocuments(
          cover_url = COALESCE(documents.cover_url, excluded.cover_url),
          page_count = COALESCE(documents.page_count, excluded.page_count),
          language = COALESCE(documents.language, excluded.language),
+         -- Genres set by hand beat Hardcover's; otherwise the kept document's win.
+         genres = CASE WHEN excluded.genres_manual AND NOT documents.genres_manual THEN excluded.genres
+                       ELSE COALESCE(documents.genres, excluded.genres) END,
+         genres_manual = MAX(documents.genres_manual, excluded.genres_manual),
          updated_at = excluded.updated_at`
     ).run(into, now, userId, from);
     db.prepare('DELETE FROM documents WHERE user_id = ? AND document = ?').run(userId, from);
diff --git a/src/routes/v1/documents.ts b/src/routes/v1/documents.ts
index 10477f7..ca59ced 100644
--- a/src/routes/v1/documents.ts
+++ b/src/routes/v1/documents.ts
@@ -271,10 +271,10 @@ export function documentRoutes(db: DB, http?: HttpTransport): Hono<AppEnv> {
     return c.json({ items: await coverCandidates(http ?? fetchTransport, title, q ? '' : (meta?.author ?? '')) });
   });
 
-  // Manual cover / print page count / title and author / language when lookups got it wrong.
+  // Manual cover / print page count / title and author / language / genres when lookups got it wrong.
   // Manual values stick (lookups only fill blanks, and device syncs don't replace an
-  // edited title or language); null clears cover or page count so it's looked up again,
-  // and language so the next device sync fills it.
+  // edited title or language); null clears cover, page count or genres so they're looked
+  // up again, and language so the next device sync fills it.
   app.put('/documents/:document/info', async (c) => {
     const param = c.req.param('document');
     let body: unknown;
@@ -290,12 +290,17 @@ export function documentRoutes(db: DB, http?: HttpTransport): Hono<AppEnv> {
     const title = text(o.title);
     const author = text(o.author);
     const language = o.language === undefined || o.language === null ? o.language : languageTag(o.language);
+    // Same shape Hardcover's genres are stored in: a short list of short names.
+    const genres = Array.isArray(o.genres) ? [...new Set(o.genres.map(text))] : o.genres;
+    const genresOk =
+      genres === undefined || genres === null ||
+      (Array.isArray(genres) && genres.length <= 10 && genres.every((g) => typeof g === 'string' && g.length > 0 && g.length <= 64));
     // A title is required once edited; an empty author means "no author".
     const titleOk = title === undefined || (typeof title === 'string' && title.length > 0);
     const authorOk = author === undefined || typeof author === 'string';
     const coverOk = cover === undefined || cover === null || (typeof cover === 'string' && /^https?:\/\/\S{1,2000}$/.test(cover));
     const pagesOk = pages === undefined || pages === null || (Number.isInteger(pages) && (pages as number) > 0 && (pages as number) <= 100000);
-    if (!isValidDocument(param) || !coverOk || !pagesOk || !titleOk || !authorOk || (language === null && o.language !== null)) {
+    if (!isValidDocument(param) || !coverOk || !pagesOk || !titleOk || !authorOk || !genresOk || (language === null && o.language !== null)) {
       return kosyncError(c, 403, 2003, 'Invalid request');
     }
     const user = c.get('user');
@@ -311,6 +316,14 @@ export function documentRoutes(db: DB, http?: HttpTransport): Hono<AppEnv> {
     if (language !== undefined) {
       db.prepare('UPDATE documents SET language = ? WHERE user_id = ? AND document = ?').run(language as string | null, user.id, document);
     }
+    if (genres !== undefined) {
+      const list = genres as string[] | null;
+      // Clearing hands genres back to Hardcover: the next enrichment pass looks the book up again.
+      db.prepare(
+        `UPDATE documents SET genres = ?, genres_manual = ?, hc_checked_at = CASE WHEN ? THEN hc_checked_at ELSE NULL END
+         WHERE user_id = ? AND document = ?`
+      ).run(list?.length ? JSON.stringify(list) : null, list ? 1 : 0, list ? 1 : 0, user.id, document);
+    }
     if (title !== undefined || author !== undefined) {
       // New title/author: everything found with the old one is looked up again
       // (blank cover and page count, Hardcover details, automatic service matches).
@@ -322,10 +335,11 @@ export function documentRoutes(db: DB, http?: HttpTransport): Hono<AppEnv> {
       ).run((title as string | undefined) ?? null, author !== undefined ? 1 : 0, (author as string | undefined) ?? '', user.id, document);
       db.prepare("DELETE FROM connector_matches WHERE user_id = ? AND document = ? AND source IN ('auto', 'none')").run(user.id, document);
     }
-    const row = db.prepare('SELECT cover_url, page_count, title, author, language FROM documents WHERE user_id = ? AND document = ?').get(user.id, document) as {
-      cover_url: string | null; page_count: number | null; title: string | null; author: string | null; language: string | null;
+    const row = db.prepare('SELECT cover_url, page_count, title, author, language, genres FROM documents WHERE user_id = ? AND document = ?').get(user.id, document) as {
+      cover_url: string | null; page_count: number | null; title: string | null; author: string | null; language: string | null; genres: string | null;
     };
-    return c.json({ document, cover_url: row.cover_url, page_count: row.page_count, title: row.title, author: row.author, language: row.language });
+    return c.json({ document, cover_url: row.cover_url, page_count: row.page_count, title: row.title, author: row.author, language: row.language,
+      genres: row.genres ? (JSON.parse(row.genres) as string[]) : [] });
   });
 
   app.get('/documents', (c) => {
diff --git a/test/manual-genres.test.ts b/test/manual-genres.test.ts
new file mode 100644
index 0000000..8eeda61
--- /dev/null
+++ b/test/manual-genres.test.ts
@@ -0,0 +1,76 @@
+import { beforeEach, describe, expect, it } from 'vitest';
+import type { HttpTransport } from '../src/connectors/types.js';
+import { documentInfo } from '../src/models/cover.js';
+import { resetHardcoverThrottle } from '../src/models/hardcover-catalog.js';
+import { DOC, makeTestApp, registerUser } from './helpers.js';
+
+// Hardcover finds the book with its own genres; the free cover sources find nothing.
+const hardcover: HttpTransport = async (url) => {
+  const hit = { id: '41398', slug: 'foundryside', title: 'Foundryside', author_names: ['Robert Jackson Bennett'], genres: ['Fantasy', 'Magic'] };
+  const body = url.includes('hardcover') ? { data: { search: { results: { hits: [{ document: hit }] } } } } : {};
+  return { status: 200, text: async () => JSON.stringify(body), json: async () => body };
+};
+
+beforeEach(() => resetHardcoverThrottle());
+
+describe('manual genres', () => {
+  it('sticks over Hardcover lookups and clears back to them', async () => {
+    const { app, db } = makeTestApp();
+    const { username, headers } = await registerUser(app);
+    await app.request('/syncs/progress', {
+      method: 'PUT',
+      headers,
+      body: JSON.stringify({ document: DOC, progress: '/body/DocFragment[2]', percentage: 0.2, device: 'X4', device_id: 'x4',
+        metadata: { title: 'Foundryside', authors: 'Robert Jackson Bennett' } }),
+    });
+    const { id } = db.prepare('SELECT id FROM users WHERE username = ?').get(username) as { id: number };
+    const put = (body: unknown) => app.request(`/api/v1/documents/${DOC}/info`, { method: 'PUT', headers, body: JSON.stringify(body) });
+    const listed = async () => ((await (await app.request('/api/v1/progress', { headers })).json()) as { items: { genres: string[] }[] }).items[0].genres;
+    const enrich = () => documentInfo(db, id, DOC, hardcover, { HARDCOVER_API_KEY: 'k' }, { hardcover: true });
+
+    expect((await put({ genres: 'Fantasy' })).status).toBe(403);
+    expect((await put({ genres: [''] })).status).toBe(403);
+    expect((await put({ genres: ['x'.repeat(65)] })).status).toBe(403);
+    expect((await put({ genres: Array.from({ length: 11 }, (_, i) => `g${i}`) })).status).toBe(403);
+
+    // Trimmed and de-duplicated, and back in the book list.
+    expect(await (await put({ genres: [' Heist ', 'Heist', 'Fantasy'] })).json()).toMatchObject({ genres: ['Heist', 'Fantasy'] });
+    expect(await listed()).toEqual(['Heist', 'Fantasy']);
+
+    // Hardcover's lookup fills the other details but leaves the genres alone.
+    await enrich();
+    expect(await listed()).toEqual(['Heist', 'Fantasy']);
+    expect(db.prepare('SELECT hc_slug FROM documents WHERE document = ?').get(DOC)).toEqual({ hc_slug: 'foundryside' });
+
+    // null hands them back: the next lookup brings Hardcover's genres.
+    expect(await (await put({ genres: null })).json()).toMatchObject({ genres: [] });
+    await enrich();
+    expect(await listed()).toEqual(['Fantasy', 'Magic']);
+
+    // Other info edits don't touch manual genres.
+    await put({ genres: ['Heist'] });
+    await put({ page_count: 500 });
+    expect(await listed()).toEqual(['Heist']);
+  });
+
+  it('keeps manual genres through a merge, over Hardcover\'s', async () => {
+    const { app, db } = makeTestApp();
+    const { headers } = await registerUser(app);
+    const OTHER = 'ffffffffffffffffffffffffffffffff';
+    for (const document of [DOC, OTHER]) {
+      await app.request('/syncs/progress', {
+        method: 'PUT',
+        headers,
+        body: JSON.stringify({ document, progress: '/body/DocFragment[2]', percentage: 0.2, device: 'X4', device_id: 'x4',
+          metadata: { title: 'Foundryside', authors: 'Robert Jackson Bennett' } }),
+      });
+    }
+    // The kept book only has Hardcover's genres; the merged-away one has some set by hand.
+    db.prepare('UPDATE documents SET genres = ? WHERE document = ?').run('["Fantasy"]', DOC);
+    await app.request(`/api/v1/documents/${OTHER}/info`, { method: 'PUT', headers, body: JSON.stringify({ genres: ['Heist'] }) });
+
+    const merge = await app.request('/api/v1/documents/merge', { method: 'POST', headers, body: JSON.stringify({ document: OTHER, into: DOC }) });
+    expect(merge.status).toBe(200);
+    expect(db.prepare('SELECT genres, genres_manual FROM documents WHERE document = ?').get(DOC)).toEqual({ genres: '["Heist"]', genres_manual: 1 });
+  });
+});