diff --git a/bookish/static/css/style.css b/bookish/static/css/style.css
index f494252..9cd4069 100644
--- a/bookish/static/css/style.css
+++ b/bookish/static/css/style.css
@@ -465,6 +465,134 @@ body {
     font-variant-numeric: tabular-nums;
 }
 
+/* Help button */
+.btn-help {
+    width: 26px;
+    height: 26px;
+    padding: 0;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    border-radius: 50%;
+    font-size: 0.85rem;
+    font-weight: 700;
+    color: #888;
+    background: #f5f5f7;
+    border: 1px solid #ddd;
+    cursor: pointer;
+    transition: all 0.2s;
+}
+
+.btn-help:hover {
+    background: #007aff;
+    color: #fff;
+    border-color: #007aff;
+}
+
+/* Help overlay modal */
+.help-overlay {
+    display: none;
+    position: fixed;
+    inset: 0;
+    background: rgba(0,0,0,0.35);
+    z-index: 200;
+    align-items: center;
+    justify-content: center;
+}
+
+.help-overlay.open {
+    display: flex;
+}
+
+.help-modal {
+    background: #fff;
+    border-radius: 14px;
+    width: min(440px, 90vw);
+    max-height: min(520px, 80vh);
+    display: flex;
+    flex-direction: column;
+    box-shadow: 0 12px 40px rgba(0,0,0,0.2);
+    overflow: hidden;
+}
+
+.help-header {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    padding: 1rem 1.2rem;
+    border-bottom: 1px solid #eee;
+}
+
+.help-header h3 {
+    margin: 0;
+    font-size: 1rem;
+    font-weight: 600;
+}
+
+.help-body {
+    padding: 0.8rem 1.2rem 1.2rem;
+    overflow-y: auto;
+}
+
+.help-section {
+    margin-bottom: 1rem;
+}
+
+.help-section h4 {
+    font-size: 0.8rem;
+    font-weight: 600;
+    color: #007aff;
+    text-transform: uppercase;
+    letter-spacing: 0.04em;
+    margin: 0 0 0.5rem;
+}
+
+.help-section p {
+    margin: 0;
+    font-size: 0.85rem;
+    color: #555;
+    line-height: 1.5;
+}
+
+.help-row {
+    display: flex;
+    align-items: center;
+    gap: 0.4rem;
+    padding: 0.3rem 0;
+    font-size: 0.85rem;
+    color: #333;
+}
+
+.help-row span:last-child {
+    color: #555;
+}
+
+.help-row kbd {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    min-width: 24px;
+    padding: 1px 6px;
+    font-size: 0.7rem;
+    font-family: inherit;
+    background: #f0f0f0;
+    border: 1px solid #d0d0d5;
+    border-radius: 4px;
+    box-shadow: 0 1px 0 #ccc;
+    color: #444;
+}
+
+.help-icon {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    width: 22px;
+    height: 22px;
+    font-size: 0.75rem;
+    background: #f0f0f0;
+    border-radius: 4px;
+}
+
 /* Reader Layout */
 .reader-container {
     display: flex;
diff --git a/bookish/static/js/reader.js b/bookish/static/js/reader.js
index 26eff62..4e1a7ca 100644
--- a/bookish/static/js/reader.js
+++ b/bookish/static/js/reader.js
@@ -307,6 +307,31 @@
             });
         }
 
+        // Help modal toggle
+        const helpToggle = document.getElementById("helpToggle");
+        const helpOverlay = document.getElementById("helpOverlay");
+        const helpClose = document.getElementById("helpClose");
+        function toggleHelp(show) {
+            if (!helpOverlay) return;
+            if (show === undefined) show = !helpOverlay.classList.contains("open");
+            helpOverlay.classList.toggle("open", show);
+        }
+        if (helpToggle) {
+            helpToggle.addEventListener("click", () => toggleHelp(true));
+        }
+        if (helpClose) {
+            helpClose.addEventListener("click", () => toggleHelp(false));
+        }
+        if (helpOverlay) {
+            helpOverlay.addEventListener("click", (e) => {
+                if (e.target === helpOverlay) toggleHelp(false);
+            });
+        }
+        // Keyboard: Esc to close help
+        document.addEventListener("keydown", (e) => {
+            if (e.key === "Escape") toggleHelp(false);
+        });
+
         // Bookmark button
         const bookmarkToggle = document.getElementById("bookmarkToggle");
         if (bookmarkToggle) {
diff --git a/bookish/templates/reader.html b/bookish/templates/reader.html
index 7c0c983..c0cd470 100644
--- a/bookish/templates/reader.html
+++ b/bookish/templates/reader.html
@@ -28,6 +28,36 @@
             <button class="tool-btn" id="searchToggle" title="Cerca">🔍</button>
             <button class="tool-btn" id="bookmarkToggle" title="Segnalibro (Ctrl+B)">🔖</button>
             <button class="tool-btn" id="fullscreenToggle" title="Schermo intero">⛶</button>
+            <button class="tool-btn btn-help" id="helpToggle" title="Aiuto e scorciatoie">?</button>
+        </div>
+    </div>
+
+    <div class="help-overlay" id="helpOverlay">
+        <div class="help-modal">
+            <div class="help-header">
+                <h3>Aiuto e scorciatoie</h3>
+                <button class="tool-btn" id="helpClose">✕</button>
+            </div>
+            <div class="help-body">
+                <div class="help-section">
+                    <h4>Navigazione</h4>
+                    <div class="help-row"><kbd>←</kbd><kbd>→</kbd><span>Pagina precedente/successiva</span></div>
+                    <div class="help-row"><kbd>Ctrl</kbd>+<kbd>B</kbd><span>Aggiungi/rimuovi segnalibro</span></div>
+                    <div class="help-row"><kbd>Ctrl</kbd>+<kbd>F</kbd><span>Cerca nel libro</span></div>
+                    <div class="help-row"><kbd>F</kbd><span>Schermo intero</span></div>
+                </div>
+                <div class="help-section">
+                    <h4>Lettura</h4>
+                    <div class="help-row"><kbd>+</kbd><kbd>-</kbd><span>Zoom avanti/indietro (testo)</span></div>
+                    <div class="help-row"><span class="help-icon">☰</span><span>Mostra/nascondi indice</span></div>
+                    <div class="help-row"><span class="help-icon">🔖</span><span>Aggiunge segnalibro alla pagina corrente</span></div>
+                    <div class="help-row"><span class="help-icon">🌙 ☀️ 🟤</span><span>Cicla tema: chiaro, scuro, seppia</span></div>
+                </div>
+                <div class="help-section">
+                    <h4>Slider larghezza</h4>
+                    <p>Regola la larghezza dell'area di lettura dal 40% al 100% dello schermo. Utile per files con righe molto lunghe.</p>
+                </div>
+            </div>
         </div>
     </div>