Now see what happens persisting the Author entities of the books:

Author luca_stancapiano = new Author("Luca Stancapiano");
Author davide_barillari = new Author("Davide Barillari");
Author davide_scala = new Author("Davide Scala");
Book wildfly_book = new Book("Mastering Java EE Development with WildFly 10");
Book maledetti_grillini = new Book("Maledetti grillini");
luca_stancapiano.addBook(wildfly_book);
davide_barillari.addBook(wildfly_book);
luca_stancapiano.addBook(maledetti_grillini);
davide_barillari.addBook(maledetti_grillini);
davide_scala.addBook(maledetti_grillini);
entityManager.persist(luca_stancapiano);
entityManager.persist(davide_barillari);
entityManager.persist(davide_scala);

The Book and the Book_Author rows will be inserted automatically together with the Authors:

insert into Author (id, full_name) values (default, 'Luca Stancapiano')
insert into Book (id, title) values (default, 'Mastering Java EE Development with WildFly 10')
insert into Author (id, full_name) values (default, 'Davide Barillari')
insert into Book (id, title) values (default, 'Maledetti grillini')
insert into Author (id, full_name) values (default, 'Davide Scala')
insert into Book_Author (book_id, author_id) values (1, 1)
insert into Book_Author (book_id, author_id) values (1, 2)
insert into Book_Author (book_id, author_id) values (2, 1)
insert into Book_Author (book_id, author_id) values (2, 2)
insert into Book_Author (book_id, author_id) values (2, 3)