Here are the list of some good e books if you want to purchase online. This books are really comprehensive and have significant in dept study materials which will help you to kick start your drupal 7 project and build professional websites in a minute.
Amazon.com have a great collection of drupal 7 e books. You can order them online or read offline. Just checkout the links for more.
Go to amazon.com and there you will find more ebooks on latest drupal development techniques written by experts.