I like the Barron's book for pictures, but I find that it's a little biased, like the author based his info on observing his own pet hedgehog, but it doesn't apply to all hedgehogs. For example, the book says that hedgehogs can't be
litter trained, but a lot of them can. I found an interesting book on ebay called "The Natural Hedgehog". It isn't too useful for learning about pygmy hedgehogs as pets, but was written about caring for wild (European) hedgehogs that you find injured. It has really nice diagrams and info on hedgehogs of the world. It also has a lot of methods of keeping a hedgehog healthy with natural and holistic means, which can also be applied to pet hedgehogs.