If you're interested in zen, this is a zen meditation book that we use at our dojo, it has a lot of diagrams and instructions, but I think one would still need some class instruction to really get good correction...if you sit crookedly for any length of time it really starts to hurt...
An Introduction to Zen Training: A Translation of Sanzen Nyumon
by Omori Sogen, Trevor Leggett (Introduction), Dogen Hosokawa (Translator), Roy Kenichi Yoshimoto (Translator), Dogen Hosogawa (Translator)