The Tessellations File by Chris de Cordova

The majority of this book is a set of 40 black and white line drawings of tessalations increasing in complexity which are free to photocopy and useful for parents and teachers alike.

However, at the beginning there is an excellent 8 page introduction by de Cordova on tessellations, how they work and how to extend the basics to create tessellations of your own, along with a short bibliography.  Good if you're a bit mystified by the maths of the whole thing.