diff --git a/server/src/modules/book/book-query-builder.service.test.ts b/server/src/modules/book/book-query-builder.service.test.ts
index 5106c32f5..c6d87134e 100644
--- a/server/src/modules/book/book-query-builder.service.test.ts
+++ b/server/src/modules/book/book-query-builder.service.test.ts
@@ -1901,8 +1901,13 @@ describe('BookQueryBuilder.buildCollapseOrderBy', () => {
     expect(BookQueryBuilder.buildCollapseOrderBy([{ field: 'title', dir: 'desc' }], 1)).toBe('sort_title DESC NULLS LAST, r.id ASC');
   });
 
-  it('generates sort_title for series field', () => {
-    expect(BookQueryBuilder.buildCollapseOrderBy([{ field: 'series', dir: 'asc' }], 1)).toBe('sort_title ASC NULLS LAST, r.id ASC');
+  it('orders series stacks before standalone books, then by title, in both directions', () => {
+    expect(BookQueryBuilder.buildCollapseOrderBy([{ field: 'series', dir: 'asc' }], 1)).toBe(
+      'sort_series ASC NULLS LAST, sort_title ASC NULLS LAST, r.id ASC',
+    );
+    expect(BookQueryBuilder.buildCollapseOrderBy([{ field: 'series', dir: 'desc' }], 1)).toBe(
+      'sort_series DESC NULLS LAST, sort_title DESC NULLS LAST, r.id ASC',
+    );
   });
 
   it('generates sort_added_at for addedAt field', () => {
@@ -1934,7 +1939,7 @@ describe('BookQueryBuilder.buildCollapseOrderBy', () => {
       1,
     );
     expect(result).toContain("split_part(series_index::text, '.', 1)::numeric");
-    expect(result).toContain('series_index COLLATE "C" ASC NULLS LAST, sort_title ASC NULLS LAST, r.id ASC');
+    expect(result).toContain('series_index COLLATE "C" ASC NULLS LAST, sort_series ASC NULLS LAST, sort_title ASC NULLS LAST, r.id ASC');
   });
 
   it('generates user-scoped subquery for readProgress', () => {
diff --git a/server/src/modules/book/book-query-builder.service.ts b/server/src/modules/book/book-query-builder.service.ts
index 60460e304..66b333164 100644
--- a/server/src/modules/book/book-query-builder.service.ts
+++ b/server/src/modules/book/book-query-builder.service.ts
@@ -1135,7 +1135,12 @@ export class BookQueryBuilder {
       }
       switch (field) {
         case 'title':
+          parts.push(`sort_title ${D} NULLS LAST`);
+          break;
+        // sort_series is NULL for standalone books, so series stacks lead in both directions
+        // and the standalones that follow are ordered by title.
         case 'series':
+          parts.push(`sort_series ${D} NULLS LAST`);
           parts.push(`sort_title ${D} NULLS LAST`);
           break;
         case 'addedAt':
diff --git a/server/src/modules/book/book.repository.ts b/server/src/modules/book/book.repository.ts
index 29cf60e24..7f594652e 100644
--- a/server/src/modules/book/book.repository.ts
+++ b/server/src/modules/book/book.repository.ts
@@ -98,6 +98,7 @@ type CollapsedRawRow = {
   publisher: string | null;
   page_count: number | null;
   sort_title: string | null;
+  sort_series: string | null;
   sort_added_at: string | null;
   book_count: string | null;
   read_count: string | null;
@@ -239,8 +240,10 @@ function collapsedDiscreteSourceParts(field: SortField, userId: number): Collaps
 
   switch (field) {
     case 'title':
-    case 'series':
       return direct(sql.raw('r.sort_title'));
+    // Standalone books have no series letter, matching the flat rail.
+    case 'series':
+      return direct(sql.raw('r.sort_series'));
     case 'author':
       return direct(sql.raw('r.author_sort_name'));
     case 'publisher':
@@ -1079,6 +1082,7 @@ export class BookRepository {
           base.metadata_score,
           base.primary_author_sort_name AS author_sort_name,
           COALESCE(base.norm_series, lower(base.title)) AS sort_title,
+          base.norm_series AS sort_series,
           COALESCE(sa.latest_added_at, base.added_at) AS sort_added_at,
           COALESCE(sa.first_collection_position, base.collection_position) AS sort_collection_position,
           sa.book_count,
@@ -1311,6 +1315,7 @@ export class BookRepository {
           ubr.rating,
           base.primary_author_sort_name AS author_sort_name,
           COALESCE(base.norm_series, lower(base.title)) AS sort_title,
+          base.norm_series AS sort_series,
           COALESCE(sl.latest_added_at, base.added_at) AS sort_added_at
           ${source.representativeExtraSelect}
         FROM base_rows base
diff --git a/server/test/jump-buckets-invariant.e2e-spec.ts b/server/test/jump-buckets-invariant.e2e-spec.ts
index 8a34a2690..332ce9227 100644
--- a/server/test/jump-buckets-invariant.e2e-spec.ts
+++ b/server/test/jump-buckets-invariant.e2e-spec.ts
@@ -57,7 +57,7 @@ function expectedBucketKey(
     return String(Math.floor(book.publishedYear / step) * step);
   }
   if (field === 'author') return letterOf(book.authorSortName);
-  if (field === 'series') return letterOf(collapsed ? (book.seriesName ?? book.title) : book.seriesName);
+  if (field === 'series') return letterOf(book.seriesName);
   if (field === 'publisher') return letterOf(book.publisher);
   if (collapsed) return letterOf(book.seriesName ?? book.title);
   return letterOf(book.title);
@@ -412,6 +412,25 @@ describe('Jump buckets invariant (e2e)', { timeout: SCENARIO_TIMEOUT_MS }, () =>
     }
   });
 
+  for (const dir of dirs) {
+    it(`lists collapsed series stacks before standalone books by title when sorting by series ${dir}`, async () => {
+      const [seriesListing, titleListing] = await Promise.all([
+        fetchListing([{ field: 'series', dir }], true),
+        fetchListing([{ field: 'title', dir }], true),
+      ]);
+      const rows = seriesListing.items.map((item) => seededById.get((item as BookCard).id)!);
+      const firstStandalone = rows.findIndex((row) => row.seriesName === null);
+
+      expect(rows.slice(0, firstStandalone).map((row) => row.seriesName)).toEqual(
+        dir === 'asc' ? ['Dune Saga', 'zeta chronicles'] : ['zeta chronicles', 'Dune Saga'],
+      );
+      expect(rows.slice(firstStandalone).every((row) => row.seriesName === null)).toBe(true);
+      expect(rows.slice(firstStandalone).map((row) => row.id)).toEqual(
+        titleListing.items.map((item) => (item as BookCard).id).filter((id) => seededById.get(id)!.seriesName === null),
+      );
+    });
+  }
+
   it('preserves every populated year when sparse years fit the bounded capacity', async () => {
     const response = await fetchBuckets([{ field: 'publishedYear', dir: 'asc' }], false);
     const expectedYears = [...new Set([...seededById.values()].flatMap((book) => (book.publishedYear === null ? [] : [String(book.publishedYear)])))];