You can only take a look to a short preview of your book by clicking the "See inside!" button (The button will appear once the computation of the number of pages is over). 

However, you can check and edit the complete list of posts. To do that go In the creation page, and scroll down to see the "edit content" button. Click on it and you will be able to see each post that will be printed in the book, and check or uncheck whatever you want.