diff --git a/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/BookInfo.java b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/BookInfo.java
new file mode 100644
index 0000000..d90e431
--- /dev/null
+++ b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/BookInfo.java
@@ -0,0 +1,14 @@
+package fr.iut_fbleau.but3.dev62.mylibrary.book;
+
+import java.time.LocalDate;
+
+public record BookInfo(
+    String isbn,
+    String title,
+    String author,
+    String publisher,
+    LocalDate publicationDate,
+    double price,
+    int stockInitial
+) {
+}
diff --git a/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/entity/Book.java b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/entity/Book.java
new file mode 100644
index 0000000..35f9c18
--- /dev/null
+++ b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/entity/Book.java
@@ -0,0 +1,29 @@
+package fr.iut_fbleau.but3.dev62.mylibrary.book.entity;
+
+import fr.iut_fbleau.but3.dev62.mylibrary.customer.exception.IllegalCustomerPointException;
+
+import java.rmi.server.UID;
+import java.time.LocalDate;
+import java.util.UUID;
+
+import lombok.Builder;
+import lombok.Getter;
+
+@Builder
+@Getter
+
+public class Book {
+  //private UUID id;
+  private String isbn;
+  private String title;
+  private String author;
+  private String publisher;
+  private LocalDate publicationDate;
+  private double price;
+  private int stock;
+}
+/* 
+public void setRandomUUID() {
+  this.id = UUID.randomUUID();
+}
+*/
\ No newline at end of file
diff --git a/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/exception/BookNotFoundException.java b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/exception/BookNotFoundException.java
new file mode 100644
index 0000000..d62cb3d
--- /dev/null
+++ b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/exception/BookNotFoundException.java
@@ -0,0 +1,14 @@
+package fr.iut_fbleau.but3.dev62.mylibrary.book.exception;
+
+import java.text.MessageFormat;
+import java.util.UUID;
+
+public class BookNotFoundException {
+
+    public static final String THE_BOOK_WITH_ID_DOES_NOT_EXISTS = "The book with id {0} does not exist";
+
+    public BookNotFoundException(UUID uuid) {
+        super(); //super(MessageFormat.format(THE_BOOK_WITH_ID_DOES_NOT_EXISTS, uuid)); à corriger
+    }
+    
+}
\ No newline at end of file
diff --git a/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/exception/NotValidBookException.java b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/exception/NotValidBookException.java
new file mode 100644
index 0000000..6eab151
--- /dev/null
+++ b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/exception/NotValidBookException.java
@@ -0,0 +1,8 @@
+package fr.iut_fbleau.but3.dev62.mylibrary.book.exception;
+
+public class NotValidBookException extends Exception {
+
+  public NotValidBookException(String message) {
+    super(message);
+  }
+}
diff --git a/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/repository/BookRepository.java b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/repository/BookRepository.java
new file mode 100644
index 0000000..c5b1c05
--- /dev/null
+++ b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/repository/BookRepository.java
@@ -0,0 +1,32 @@
+package fr.iut_fbleau.but3.dev62.mylibrary.book.repository;
+
+import fr.iut_fbleau.but3.dev62.mylibrary.book.entity.Book;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import lombok.NoArgsConstructor;
+
+@NoArgsConstructor
+public final class BookRepository {
+  private final List<Book> books = new ArrayList<>();
+
+  public Book save(Book newBook) {
+    this.findByIsbn(newBook.getIsbn()).ifPresent(books::remove);
+    this.books.add(newBook);
+    return newBook;
+  }
+
+  public Optional<Book> findByIsbn(String isbn) {
+    return this.books.stream()
+        .filter(book -> book.getIsbn().equals(isbn))
+        .findFirst();
+  }
+
+  public List<Book> findAll() {
+    return books;
+  }
+
+  public void deleteAll() {
+    books.clear();
+  }
+}
diff --git a/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/usecase/BookUseCase.java b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/usecase/BookUseCase.java
new file mode 100644
index 0000000..5d9142e
--- /dev/null
+++ b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/usecase/BookUseCase.java
@@ -0,0 +1,31 @@
+package fr.iut_fbleau.but3.dev62.mylibrary.book.usecase;
+
+import fr.iut_fbleau.but3.dev62.mylibrary.book.BookInfo;
+import fr.iut_fbleau.but3.dev62.mylibrary.book.entity.Book;
+import fr.iut_fbleau.but3.dev62.mylibrary.book.exception.NotValidBookException;
+import fr.iut_fbleau.but3.dev62.mylibrary.book.repository.BookRepository;
+import fr.iut_fbleau.but3.dev62.mylibrary.book.validator.BookValidator;
+
+public final class BookUseCase {
+
+  private final BookRepository bookRepository;
+
+  public BookUseCase(BookRepository bookRepository) {
+    this.bookRepository = bookRepository;
+  }
+
+  public String registerNewBook(BookInfo newBook) throws NotValidBookException {
+    BookValidator.validate(newBook);
+    Book bookToSave = Book.builder()
+        .isbn(newBook.isbn())
+        .title(newBook.title())
+        .author(newBook.author())
+        .publisher(newBook.publisher())
+        .publicationDate(newBook.publicationDate())
+        .price(newBook.price())
+        .stock(newBook.stockInitial())
+        .build();
+    Book savedBook = bookRepository.save(bookToSave);
+    return savedBook.getIsbn();
+  }
+}
diff --git a/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/validator/BookValidator.java b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/validator/BookValidator.java
new file mode 100644
index 0000000..4a342cf
--- /dev/null
+++ b/src/main/java/fr/iut_fbleau/but3/dev62/mylibrary/book/validator/BookValidator.java
@@ -0,0 +1,38 @@
+package fr.iut_fbleau.but3.dev62.mylibrary.book.validator;
+
+import fr.iut_fbleau.but3.dev62.mylibrary.book.BookInfo;
+import fr.iut_fbleau.but3.dev62.mylibrary.book.exception.NotValidBookException;
+
+public final class BookValidator {
+
+  private BookValidator() {
+  }
+
+  public static void validate(BookInfo bookInfo) throws NotValidBookException {
+    if (bookInfo == null) {
+      throw new NotValidBookException("Book cannot be null");
+    }
+    if (isBlank(bookInfo.isbn())) {
+      throw new NotValidBookException("ISBN is required");
+    }
+    if (isBlank(bookInfo.title())) {
+      throw new NotValidBookException("Title is required");
+    }
+    if (isBlank(bookInfo.author())) {
+      throw new NotValidBookException("Author is required");
+    }
+    if (isBlank(bookInfo.publisher())) {
+      throw new NotValidBookException("Publisher is required");
+    }
+    if (bookInfo.price() <= 0) {
+      throw new NotValidBookException("Price must be positive");
+    }
+    if (bookInfo.stockInitial() < 0) {
+      throw new NotValidBookException("Stock must be greater or equal to 0");
+    }
+  }
+
+  private static boolean isBlank(String value) {
+    return value == null || value.isBlank();
+  }
+}
diff --git a/src/test/java/fr/iut_fbleau/but3/dev62/mylibrary/book/usecase/BookUseCaseTest.java b/src/test/java/fr/iut_fbleau/but3/dev62/mylibrary/book/usecase/BookUseCaseTest.java
new file mode 100644
index 0000000..2853d90
--- /dev/null
+++ b/src/test/java/fr/iut_fbleau/but3/dev62/mylibrary/book/usecase/BookUseCaseTest.java
@@ -0,0 +1,87 @@
+package fr.iut_fbleau.but3.dev62.mylibrary.book.usecase;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import fr.iut_fbleau.but3.dev62.mylibrary.book.BookInfo;
+import fr.iut_fbleau.but3.dev62.mylibrary.book.entity.Book;
+import fr.iut_fbleau.but3.dev62.mylibrary.book.exception.NotValidBookException;
+import fr.iut_fbleau.but3.dev62.mylibrary.book.repository.BookRepository;
+import java.time.LocalDate;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class BookUseCaseTest {
+
+  @Mock
+  private BookRepository bookRepository;
+
+  @InjectMocks
+  private BookUseCase bookUseCase;
+
+  @Nested
+  @DisplayName("Register new book tests")
+  class RegisterNewBookTests {
+
+    @Test
+    @DisplayName("Should register a new book and return ISBN")
+    void shouldRegisterBookAndReturnIsbn() throws NotValidBookException {
+      BookInfo validBookInfo = new BookInfo(
+          "9783161484100",
+          "Clean Code",
+          "Robert C. Martin",
+          "Prentice Hall",
+          LocalDate.of(2008, 8, 1),
+          42.50,
+          10
+      );
+
+      Book savedBook = Book.builder()
+          .isbn("9783161484100")
+          .title("Clean Code")
+          .author("Robert C. Martin")
+          .publisher("Prentice Hall")
+          .publicationDate(LocalDate.of(2008, 8, 1))
+          .price(42.50)
+          .stock(10)
+          .build();
+
+      when(bookRepository.save(any(Book.class))).thenReturn(savedBook);
+
+      String isbn = bookUseCase.registerNewBook(validBookInfo);
+
+      assertNotNull(isbn);
+      assertEquals("9783161484100", isbn);
+      verify(bookRepository, times(1)).save(any(Book.class));
+    }
+
+    @Test
+    @DisplayName("Should throw when required field is empty")
+    void shouldThrowWhenRequiredFieldIsEmpty() {
+      BookInfo invalidBookInfo = new BookInfo(
+          "9783161484100",
+          "",
+          "Robert C. Martin",
+          "Prentice Hall",
+          LocalDate.of(2008, 8, 1),
+          42.50,
+          10
+      );
+
+      assertThrows(NotValidBookException.class, () -> bookUseCase.registerNewBook(invalidBookInfo));
+      verify(bookRepository, never()).save(any(Book.class));
+    }
+  }
+}
diff --git a/src/test/java/fr/iut_fbleau/but3/dev62/mylibrary/customer/entity/CustomerTest.java b/src/test/java/fr/iut_fbleau/but3/dev62/mylibrary/customer/entity/CustomerTest.java
index 515187e..220c46f 100644
--- a/src/test/java/fr/iut_fbleau/but3/dev62/mylibrary/customer/entity/CustomerTest.java
+++ b/src/test/java/fr/iut_fbleau/but3/dev62/mylibrary/customer/entity/CustomerTest.java
@@ -8,6 +8,7 @@ import static org.junit.jupiter.api.Assertions.*;
 
 import java.util.UUID;
 
+
 class CustomerTest {
 
   @Test