If you just want heat, then solar thermal is the way to go.
I would say to start out with a book like The People's Power Primer by Robert A Dahse it's on his web site
GeoPathfinder and is only $10, he does a good job explaining what everything does and what you need for a small system like you might want and what you need for a larger system.
If you want to read about solar water heating then something like
Amazon.com: Solar Water Heating: A Comprehensive Guide to Solar Water and Space Heating Systems (Mother Earth News Wiser Living Series) (9780865715615): Bob Ramlow, Benjamin Nusz: Books is going to give you all the info you could ask for from someone who has worked on more real life solar hot water system then you can imagine and explains how to make them work well without fail.