Where can I find books that teach how to play the keyboard?

There are not too many books specifically for learning the keyboard. You will have much better luck looking for a piano lesson book. Try a music store, such as http://www.pianopronto.com.

I would do a search on google and type "Books about learning to play the keyboard." You should get many answers with links to amazon and other big name stores.

Amazon has a Teach Yourself To Play Electronic Keyboard for $9.95. This teaches everything you need to know to get started playing electronic keyboard now! Melody, harmony and rhythm are explained in an easy-to-understand, step-by-step system. Explains how to use chord symbols to play from pop sheet music, fake books and lead sheets. You'll learn about the "Circle of 5ths" and improvising techniques.
They also have where you can purchase  The Teach Yourself To Play Electronic Keyboard, How to Play Keyboards and Keyboard Course all together for $38.89 or you can purchase them seperatly.