I haven't really found any smart fairy books - but then, I haven't really been looking. I will pimp Jim Butcher's Dresden Files books like a two dollar whore - and they've got fairies, vampires, werewolves and pretty much anything else you can shake a stick at. I've been told The Autumn Castle by Kim Wilkins is LE AWESOME, and have it...just haven't read it yet.

Also, Jonathan Strange and Mister Norrel keeps getting really good things said about it.

Oy, I have yet to look forward to translating the rest of DM into English.