diff --git a/apps/web/src/pages/BookErrorPages.test.ts b/apps/web/src/pages/BookErrorPages.test.ts
new file mode 100644
index 0000000..5e0e65a
--- /dev/null
+++ b/apps/web/src/pages/BookErrorPages.test.ts
@@ -0,0 +1,23 @@
+import { readFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+
+describe("book missing error pages", () => {
+  it("does not render fallback books on the book detail page", () => {
+    const source = readFileSync(new URL("./BookPage.tsx", import.meta.url), "utf8");
+
+    expect(source).not.toContain("getApiFallback");
+    expect(source).toContain("setBook(null)");
+    expect(source).toContain("Livre introuvable");
+    expect(source).toContain("Ce livre n'existe pas dans le catalogue.");
+  });
+
+  it("does not open the reader with a fallback book", () => {
+    const source = readFileSync(new URL("./ReaderPage.tsx", import.meta.url), "utf8");
+
+    expect(source).not.toContain("getApiFallback");
+    expect(source).toContain("setBook(null)");
+    expect(source).toContain("reader-missing-page");
+    expect(source).toContain("Livre introuvable");
+    expect(source).toContain("Ce livre n'existe pas dans le catalogue.");
+  });
+});
diff --git a/apps/web/src/pages/BookPage.tsx b/apps/web/src/pages/BookPage.tsx
index 2e607ce..5b41915 100644
--- a/apps/web/src/pages/BookPage.tsx
+++ b/apps/web/src/pages/BookPage.tsx
@@ -1,7 +1,7 @@
 import { useEffect, useState } from "react";
 import { BookOpen, LibraryBig, RotateCcw } from "lucide-react";
 import type { BookDto, ProgressDto } from "@readabook/shared";
-import { api, getApiFallback } from "../api/client";
+import { api } from "../api/client";
 import { cleanBookDescription } from "../book/description";
 import { bookDisplayTitle, bookMetadataState, bookMetadataStateLabel, bookSeriesInfo, displayPublishedDate } from "../book/metadata";
 import { EmptyState, ErrorRibbon, FormatPill, LoadingState, Meter, Panel } from "../components/ui";
@@ -17,14 +17,17 @@ export function BookPage({ bookId }: { bookId: number }) {
     setLoading(true);
     setError(undefined);
     try {
-      const [nextBook, nextProgress] = await Promise.all([api.book(bookId), api.progress(bookId)]);
+      const nextBook = await api.book(bookId);
       setBook(nextBook);
-      setProgress(nextProgress);
-    } catch (loadError) {
-      const fallback = getApiFallback<BookDto>(loadError);
-      setBook(fallback ?? null);
+      try {
+        setProgress(await api.progress(bookId));
+      } catch {
+        setProgress(null);
+      }
+    } catch {
+      setBook(null);
       setProgress(null);
-      setError(fallback ? "Fiche chargee en mode secours." : "Fiche livre indisponible.");
+      setError("Ce livre n'existe pas dans le catalogue.");
     } finally {
       setLoading(false);
     }
@@ -43,13 +46,20 @@ export function BookPage({ bookId }: { bookId: number }) {
   if (loading && !book) return <LoadingState />;
   if (!book) {
     return (
-      <Panel>
-        <EmptyState title="Fiche introuvable" detail={error ?? "Le catalogue n'a pas renvoye cet ouvrage."} />
-        <button className="ghost-button" onClick={() => void loadBook()}>
-          <RotateCcw size={17} />
-          Reessayer
-        </button>
-      </Panel>
+      <section className="book-error-page" role="alert">
+        <Panel>
+          <EmptyState title="Livre introuvable" detail={error ?? "Le serveur n'a pas renvoye cet ouvrage."} />
+          <div className="book-card-actions">
+            <button className="ghost-button" onClick={() => navigate("/home")}>
+              Retour à l'accueil
+            </button>
+            <button className="ghost-button" onClick={() => void loadBook()}>
+              <RotateCcw size={17} />
+              Reessayer
+            </button>
+          </div>
+        </Panel>
+      </section>
     );
   }
 
diff --git a/apps/web/src/pages/HomePage.tsx b/apps/web/src/pages/HomePage.tsx
index a6f72c6..ba60c05 100644
--- a/apps/web/src/pages/HomePage.tsx
+++ b/apps/web/src/pages/HomePage.tsx
@@ -8,14 +8,12 @@ import { navigate } from "../router";
 
 export function HomePage() {
   const [state, setState] = useState<DashboardData | null>(null);
-  const [fallback, setFallback] = useState(false);
 
   useEffect(() => {
     let alive = true;
     Promise.all([api.books(), api.continueReading(), api.libraries(), api.jobs()])
       .then(([books, continueReading, libraries, jobs]) => {
         if (!alive) return;
-        setFallback(books.some((book) => book.filePath.startsWith("/library/")) && jobs.length === 1);
         setState({ books, continueReading, libraries, jobs });
       })
       .catch(() => {
@@ -50,7 +48,7 @@ export function HomePage() {
         <div>
           <p>Bibliotheque personnelle</p>
           <h1>Reprendre la lecture.</h1>
-          <span>{fallback ? "API absente ou incomplete : specimens de demonstration actifs." : "Catalogue branche sur le serveur local."}</span>
+          <span>Catalogue branche sur le serveur local.</span>
         </div>
         <button className="primary-button" onClick={() => navigate("/search")}>
           <ScanLine size={18} />
diff --git a/apps/web/src/pages/HomePageProgressScroll.test.ts b/apps/web/src/pages/HomePageProgressScroll.test.ts
index d743fe0..572dcae 100644
--- a/apps/web/src/pages/HomePageProgressScroll.test.ts
+++ b/apps/web/src/pages/HomePageProgressScroll.test.ts
@@ -28,5 +28,16 @@ describe("home progress list layout", () => {
     expect(source).not.toContain("displayPublishedDate");
     expect(source).not.toContain("book.description");
     expect(source).not.toContain("book.language");
+    expect(source).not.toContain("API absente ou incomplete");
+    expect(source).not.toContain("specimens de demonstration actifs");
+  });
+
+  it("keeps visible book grids capped to five columns", () => {
+    const styles = readFileSync(new URL("../styles/app.css", import.meta.url), "utf8");
+    const bookGrid = styles.match(/\.book-grid\s*\{[^}]+\}/)?.[0] ?? "";
+    const homeBookGrid = styles.match(/\.home-book-grid\s*\{[^}]+\}/)?.[0] ?? "";
+
+    expect(bookGrid).toContain("max-width: calc((var(--book-grid-column-min) * 5) + (var(--book-grid-gap) * 4))");
+    expect(homeBookGrid).toContain("max-width: calc((var(--book-grid-column-min) * 5) + (var(--book-grid-gap) * 4))");
   });
 });
diff --git a/apps/web/src/pages/ReaderPage.tsx b/apps/web/src/pages/ReaderPage.tsx
index 1e112cd..3b32ebb 100644
--- a/apps/web/src/pages/ReaderPage.tsx
+++ b/apps/web/src/pages/ReaderPage.tsx
@@ -1,6 +1,6 @@
 import { Component, useCallback, useEffect, useMemo, useState, type ErrorInfo, type ReactNode } from "react";
 import type { BookDto } from "@readabook/shared";
-import { api, getApiFallback } from "../api/client";
+import { api } from "../api/client";
 import { CbzReader } from "../reader/CbzReader";
 import { EpubReader } from "../reader/EpubReader";
 import { pageLocator, parseCbrPageLocator, parseCbzPageLocator, parsePdfPageLocator, pdfPagePercent } from "../reader/locators";
@@ -11,6 +11,7 @@ import { majorityVisiblePage, type ReaderMode } from "../reader/readerScroll";
 import { useReaderPreferences } from "../reader/useReaderPreferences";
 import { useReaderProgress } from "../reader/useReaderProgress";
 import { navigate } from "../router";
+import { EmptyState, LoadingState, Panel } from "../components/ui";
 
 const idleControls: ReaderControls = {
   canPrevious: false,
@@ -74,10 +75,9 @@ export function ReaderPage({ bookId }: { bookId: number }) {
     setError(undefined);
     try {
       setBook(await api.book(bookId));
-    } catch (loadError) {
-      const fallback = getApiFallback<BookDto>(loadError);
-      setBook(fallback ?? null);
-      setError(fallback ? "Lecteur ouvert en mode secours." : "Ouvrage indisponible.");
+    } catch {
+      setBook(null);
+      setError("Ce livre n'existe pas dans le catalogue.");
     } finally {
       setLoading(false);
     }
@@ -206,6 +206,26 @@ export function ReaderPage({ bookId }: { bookId: number }) {
     [changeMode, mode, supportsMode]
   );
 
+  if (loading && !book) return <LoadingState />;
+
+  if (!book) {
+    return (
+      <section className="reader-missing-page" role="alert">
+        <Panel>
+          <EmptyState title="Livre introuvable" detail={error ?? "Le serveur n'a pas renvoye cet ouvrage."} />
+          <div className="reader-error-actions">
+            <button className="ghost-button" onClick={() => navigate("/home")}>
+              Retour à l'accueil
+            </button>
+            <button className="ghost-button" onClick={() => void loadBook()}>
+              Réessayer
+            </button>
+          </div>
+        </Panel>
+      </section>
+    );
+  }
+
   return (
     <ReaderShell
       title={book?.title ?? "Ouverture du lecteur"}
@@ -251,14 +271,7 @@ export function ReaderPage({ bookId }: { bookId: number }) {
           </div>
         )}
       >
-        {!book ? (
-          <div className="reader-fallback">
-            <span>{error ?? "Chargement du livre."}</span>
-            <button className="ghost-button" onClick={() => void loadBook()}>
-              Reessayer
-            </button>
-          </div>
-        ) : book.format === "pdf" ? (
+        {book.format === "pdf" ? (
           <PdfReader
             url={fileUrl}
             page={page}
diff --git a/apps/web/src/styles/app.css b/apps/web/src/styles/app.css
index d62fa0d..bce601e 100644
--- a/apps/web/src/styles/app.css
+++ b/apps/web/src/styles/app.css
@@ -161,9 +161,13 @@ h2 {
 }
 
 .book-grid {
+  --book-grid-column-min: 240px;
+  --book-grid-gap: 16px;
   display: grid;
-  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
-  gap: 16px;
+  grid-template-columns: repeat(auto-fill, minmax(var(--book-grid-column-min), 1fr));
+  gap: var(--book-grid-gap);
+  width: 100%;
+  max-width: calc((var(--book-grid-column-min) * 5) + (var(--book-grid-gap) * 4));
 }
 
 .book-card {
@@ -237,6 +241,15 @@ h2 {
   white-space: pre-line;
 }
 
+.book-error-page,
+.reader-missing-page {
+  display: grid;
+  align-items: center;
+  width: min(100%, 680px);
+  min-height: 60vh;
+  margin: 0 auto;
+}
+
 .book-card-description {
   display: -webkit-box;
   overflow: hidden;
@@ -439,9 +452,13 @@ h2 {
 }
 
 .home-book-grid {
+  --book-grid-column-min: 190px;
+  --book-grid-gap: 14px;
   display: grid;
-  grid-template-columns: repeat(auto-fill, minmax(190px, 1fr));
-  gap: 14px;
+  grid-template-columns: repeat(auto-fill, minmax(var(--book-grid-column-min), 1fr));
+  gap: var(--book-grid-gap);
+  width: 100%;
+  max-width: calc((var(--book-grid-column-min) * 5) + (var(--book-grid-gap) * 4));
 }
 
 .home-book-card {