best wofati building info?

So I want to build a wofati in a couple years but right now I need some more information about how to build one. I got the book by Mike Oehler and i was thinking about getting the Combined Underground House Workshop and Shelter Seminar. But before I throw down $100 on it I was wondering what material is covered in it/ is it worth getting (there where no reviews or anything else on amazon). Also if anyone knows of any other good books that would be helpful with this that would be awesome (especially something on hooking up solar panels/ wiring the house). Thanks for any advice.