Those of us living in Japan can get Prime for 1600 yen from Amazon (vs 5500 yen). [ame="http://www.amazon.co.jp/Prime-The-Definitive-Digital-Collection/dp/0956817149/ref=sr_1_1?ie=UTF8&qid=1372235828&sr=8-1&keywords=Prime+digital+art+collection"]**LINK**[/ame] If you keep digging, you will find other books for 40-70% off.
do your best to avoid digital reference, learn from it but i recommend sticking with human reference to avoid copying any mistakes that could have been made in the digital ones