There is some good information in these books, but most of it is either outdated or just plain wrong. I have honestly found more valuable information here and on other forums and websites in regards to health, care, food, and housing than any of the books on the market could offer. If you do go for books, look at the year they were published; I saw one that was written in 1994!
When I bought Ivan, he came with The Hedgehog Primer (http://hedgehogvalley.com/primer.html). I thought that it had some good information, a lot of which matches with what our forum experts say. It's been pretty helpful for me.