diff --git a/debugging/book-library/index.html b/debugging/book-library/index.html
index 23acfa71..5cdc7b00 100644
--- a/debugging/book-library/index.html
+++ b/debugging/book-library/index.html
@@ -91,6 +91,6 @@ <h1>Library</h1>
       </tbody>
     </table>
 
-    <script src="script.js"></script>
+    <script src="script.js" type="module"></script>
   </body>
 </html>
diff --git a/debugging/book-library/script.js b/debugging/book-library/script.js
index 75ce6c1d..ddb735c2 100644
--- a/debugging/book-library/script.js
+++ b/debugging/book-library/script.js
@@ -1,103 +1,112 @@
+class Book {
+  constructor(title, author, pages, check) {
+    this.title = title.trim();
+    this.author = author.trim();
+    this.pages = Number(pages);
+    this.check = check;
+  }
+}
+
 let myLibrary = [];
 
-window.addEventListener("load", function (e) {
+window.addEventListener("load", function () {
   populateStorage();
   render();
 });
 
 function populateStorage() {
-  if (myLibrary.length == 0) {
-    let book1 = new Book("Robison Crusoe", "Daniel Defoe", "252", true);
-    let book2 = new Book(
+  if (myLibrary.length === 0) {
+    const book1 = new Book("Robinson Crusoe", "Daniel Defoe", 252, true);
+    const book2 = new Book(
       "The Old Man and the Sea",
       "Ernest Hemingway",
-      "127",
+      127,
       true
     );
     myLibrary.push(book1);
     myLibrary.push(book2);
-    render();
   }
 }
 
-const title = document.getElementById("title");
-const author = document.getElementById("author");
-const pages = document.getElementById("pages");
-const check = document.getElementById("check");
+const titleInput = document.getElementById("title");
+const authorInput = document.getElementById("author");
+const pagesInput = document.getElementById("pages");
+const readCheckbox = document.getElementById("check");
 
-//check the right input from forms and if its ok -> add the new book (object in array)
-//via Book function and start render function
 function submit() {
+  const titleValue = titleInput.value.trim();
+  const authorValue = authorInput.value.trim();
+  const pagesValue = Number(pagesInput.value);
+
   if (
-    title.value == null ||
-    title.value == "" ||
-    pages.value == null ||
-    pages.value == ""
+    titleValue === "" ||
+    authorValue === "" ||
+    !Number.isInteger(pagesValue) ||
+    pagesValue <= 0
   ) {
-    alert("Please fill all fields!");
+    alert("Please fill all fields and enter a whole page count greater than 0.");
     return false;
-  } else {
-    let book = new Book(title.value, title.value, pages.value, check.checked);
-    library.push(book);
-    render();
   }
-}
 
-function Book(title, author, pages, check) {
-  this.title = title;
-  this.author = author;
-  this.pages = pages;
-  this.check = check;
+  const book = new Book(
+    titleValue,
+    authorValue,
+    pagesValue,
+    readCheckbox.checked
+  );
+
+  myLibrary.push(book);
+  render();
+
+  titleInput.value = "";
+  authorInput.value = "";
+  pagesInput.value = "";
+  readCheckbox.checked = false;
 }
 
 function render() {
-  let table = document.getElementById("display");
-  let rowsNumber = table.rows.length;
-  //delete old table
-  for (let n = rowsNumber - 1; n > 0; n-- {
+  const table = document.getElementById("display");
+  const rowsNumber = table.rows.length;
+
+  for (let n = rowsNumber - 1; n > 0; n--) {
     table.deleteRow(n);
   }
-  //insert updated row and cells
-  let length = myLibrary.length;
-  for (let i = 0; i < length; i++) {
-    let row = table.insertRow(1);
-    let titleCell = row.insertCell(0);
-    let authorCell = row.insertCell(1);
-    let pagesCell = row.insertCell(2);
-    let wasReadCell = row.insertCell(3);
-    let deleteCell = row.insertCell(4);
-    titleCell.innerHTML = myLibrary[i].title;
-    authorCell.innerHTML = myLibrary[i].author;
-    pagesCell.innerHTML = myLibrary[i].pages;
-
-    //add and wait for action for read/unread button
-    let changeBut = document.createElement("button");
-    changeBut.id = i;
-    changeBut.className = "btn btn-success";
-    wasReadCell.appendChild(changeBut);
-    let readStatus = "";
-    if (myLibrary[i].check == false) {
-      readStatus = "Yes";
-    } else {
-      readStatus = "No";
-    }
-    changeBut.innerText = readStatus;
-
-    changeBut.addEventListener("click", function () {
+
+  for (let i = 0; i < myLibrary.length; i++) {
+    const row = table.insertRow(1);
+    const titleCell = row.insertCell(0);
+    const authorCell = row.insertCell(1);
+    const pagesCell = row.insertCell(2);
+    const wasReadCell = row.insertCell(3);
+    const deleteCell = row.insertCell(4);
+
+    titleCell.textContent = myLibrary[i].title;
+    authorCell.textContent = myLibrary[i].author;
+    pagesCell.textContent = myLibrary[i].pages;
+
+    const toggleReadButton = document.createElement("button");
+    toggleReadButton.className = "btn btn-success";
+    toggleReadButton.textContent = myLibrary[i].check ? "Yes" : "No";
+    wasReadCell.appendChild(toggleReadButton);
+
+    toggleReadButton.addEventListener("click", function () {
       myLibrary[i].check = !myLibrary[i].check;
       render();
     });
 
-    //add delete button to every row and render again
-    let delButton = document.createElement("button");
-    delBut.id = i + 5;
-    deleteCell.appendChild(delBut);
-    delBut.className = "btn btn-warning";
-    delBut.innerHTML = "Delete";
-    delBut.addEventListener("clicks", function () {
-      alert(`You've deleted title: ${myLibrary[i].title}`);
-      myLibrary.splice(i, 1);
+    const deleteButton = document.createElement("button");
+    deleteButton.className = "btn btn-warning";
+    deleteButton.textContent = "Delete";
+    deleteButton.dataset.index = i;
+    deleteCell.appendChild(deleteButton);
+
+    deleteButton.addEventListener("click", function (e) {
+      const index = Number(e.target.dataset.index);
+      const deletedTitle = myLibrary[index].title;
+
+      myLibrary.splice(index, 1);
       render();
+      alert(`You've deleted title: ${deletedTitle}`);
     });
   }
-}
+}
\ No newline at end of file