Official? What an odd concept. What's official? Is it only the stuff in the SRD? Or perhaps only books published by certain companies? I don't like the concept of official in an RPG because it sounds like someone is trying to tell me what I can use in my game.
Dragon books: Slayers Guide to Dragons, Dragons, and Draconic Lore. Least those are the three I know of, there may be others. I'll leave it up to the individual DMs to determine what is official or not in their games.
The book might be well done, and it might be better then these other books. There was time when Wizards was producing better books then the other people, but I don't feel that is the case anymore.