googleearth

Hacking Google Maps and Google Earth (ExtremeTech)
$29.99
good book - it was a touch too technical for me. But I learned a good amount - if you have more computer experience - its a great read

Google Earth For Dummies (For Dummies (Computer/Tech))
$24.99
I found this book extremely helpful in learning how to use Google Earth effectively, including how to use the KML language. However, since version 5 of Google Earth came out, some of the material in the book is understandably outdated. When the next version comes out, I'll buy it again!