Why do I have to log in to see certain pages?

Because many of the books in Google Book Search are still under copyright, we limit the amount of these books that you can see. To enforce these limits, we make some pages available only after you log in to a Google Account (such as a Google Mail account). If you do not already have a Google Account, you can create one now. The aim of Google Book Search is to help you discover books and learn where to buy or borrow them, not read them online from beginning to end. It is like going to a bookstore and browsing - with a Google twist.