If you are using BookId as an combined primary key, then remember to change your interface from:
public interface QueuedBookRepo extends JpaRepository<QueuedBook, Long> {
to:
public interface QueuedBookRepo extends JpaRepository<QueuedBook, BookId> {
And change the annotation @Embedded to @EmbeddedId, in your QueuedBook class like this:
public class QueuedBook implements Serializable {
@EmbeddedId
@NotNull
private BookId bookId;
...