Did you know you can get printed and bound books written by OWASP? Did you also know that these books are provided at cost? So most books are less than $10.
Check out my AppSensor Book
Here's a quick link to all OWASP Books
By the way, you should know that one of OWASP's core principles is to be "free and open". So all of these books are available in electronic copy at absolutely no cost. Why would you want a book instead of a free electronic copy? Well, sometimes its just nice to have it in book form :)