When you create a book project, iPhoto automatically names it based on information associated with the photos in the book, like an album or Event name. You can easily rename a book.
Keep in mind that the name of a book project and the text on the title page are different. The name of the book project is displayed at the top of All Pages view and in the Source list, and identifies the project in iPhoto. The title of the book is located in a text field that is displayed on the front cover of the book.