To buy the e-book edition, which is completely the same as the physical book, just search for it on your e-reader. It is available on the Kindle, the Nook, and through Apple's iTunes.
To purchase the physical book (paperback or hardback) online use one of the following links:
To purchase the book over the phone call 866-909-BOOK (2665).
The price ranges from $8.99 to $26.99 depending on the format you choose.