You should be running the final version of the Book Reviews plugin created in Chapter 4, The Power of Custom Post Types, or using the final resulting code (Chapter 4/ch4-book-reviews/ch4-book-reviews-v11.php) from the downloaded code bundle.
WordPress Plugin Development Cookbook - Second Edition
by Yannick Lefebvre
Published by
Packt Publishing, 2017
You should be running the final version of the Book Reviews plugin created in Chapter 4, The Power of Custom Post Types, or using the final resulting code (Chapter 4/ch4-book-reviews/ch4-book-reviews-v11.php) from the downloaded code bundle.