What kind of reference material would you like? Husbandry books, or something more in depth and scientific?
I've owned quite a few scorpion husbandry books, and most were pretty terrible. The only book that I'd kind of recommend is Scorpions. Complete Pet Owners Manual by Manny Rubio. It's the best of a bad bunch, but it does have some useful basic care information and some nice pictures. However, I think scorpion keeping has progressed so much since this book was written (particularly in Europe) that you may be left wanting a lot more information than what this book can offer. There are so many species available now that aren't covered, and thanks to a small number of mostly German breeders, husbandry techniques have advanced hugely making this book even more obsolete in my opinion. (Edit: I own the original edition of this book. It was updated in 2008 so it may be more relevant now)
If you would like to learn more about the science of scorpions, and also look at some nice pictures, I would recommend Scorpions of the World by Eric Ythier and Roland Stockmann. The book is written in generally easy to understand language and covers scorpion anatomy, taxonomy, venom and ecology, as well as descriptions (including pictures) and distribution of 350 species. There's also a chapter discussing the myths and legends about scorpions throughout history. It's not a cheap book to buy, but as an amateur hobbyist I found it an interesting read and I still use the book for reference.