The Indie Spotlight is a great site to check out both non-fiction and fiction books by self-published authors and independent publishers. If you've never visited, check it out:
http://www.theindiespotlight.com/
It's a sharp-looking site, very well done, and one of the great things is the variety of books they cover. It's a good site to get a feel for the book before you buy it. Edward C. Patterson & Greg Banks do a great job.