I've been wanting another book like Declare ever since I read it - annoying to find your absolute favourite genre appears to consist of exactly one book. Not that the Laundry isn't fun and good :) but there's something about how mystical Declare is, like a Crying of Lot 49 or Foucault's Pendulum but that actually wants to get somewhere with its hints of a bigger world rather than just tease the reader with them.