The Lexicon by Steve Vander Ark
I'd been waiting for this book forever. I'm heavily involved in HP fandom (yes, I'm one of those nuts that attend wacko fandom conventions), and I've been following the lawsuit between Mr. Vander Ark and Ms. Rowling for ages. I'm not going to get into the whys and wherefores about the lawsuit because I could see both sides to it. I will say that Mr. Vander Ark's website is superb and a font of knowledge for all things Potterish. Would that I could say the same thing about his book. I bought it, I'm not sorry I bought it, because sometimes it's a bitch just to turn on your laptop when you must know which Death Eaters survived the battle at Hogwarts (which I ended up finding at the Wiki page!), but I was disappointed.
The Lexicon is strictly alphabetical; which means it's set up like a dictionary. Which doesn't really work because I might have an inkling to how a word might be spelled and a vague idea about it's meaning, but in the HP world that means jack shit when you want to know a spell for tying one's shoelaces! I suppose you could look up the Latin for shoelace (I've done that!) and extrapolate from there, but the format assumes--rather conclusively--that you have a pretty accurate working knowledge of the HP world. The lack of an index is pretty damning, and I can only assume it was part of the deal between Vander Ark's publisher and Warner Bros.
For example, a listing of all the spells would seem to be a no brainer, but nope, not available. Who's in Slytherin house? You have to flip through the entire frigging book to find out who is in Slytherin. It certainly is nice to pick up this book and flip the "M"'s so that I can find out how to spell McGonagall (I always want to add another n), but it's frustrating if you want to, say, look up a list of teachers at Hogwarts. It seems like half a book. I find myself going BACK to the website because of the way this book is organized. I had anticipated that I would use this book instead of the website, and now I find that in most cases I will be returning to the website