The Book Explorer view enables you to view opening books. Opening books contain the most popular moves played in millions of positions along with the statistics for those moves and the play recommendations.
In the top right corner of the Book Explorer view you can access a number of configurations:
Manage CTG books - this brings up the CTG books dialog where you can add CTG books so they can be access in the Book Explorer view.
Book information - this allow you to see information about the book being displayed in the About book dialog
Select book - this allows you to select a book from the available books which are listed in the book list: