[Haskell-cafe] Books for "advanced" Haskell

Hi all, there seems to be a huge number of things that monads can be used for. And there are lots of papers, blog posts, etc. describing that, some more or less accessible. Apart from monads there are of course also Applicative Functors, Monoids, Arrows and what have you. But in short the Monad thingy seems to be the most "powerful" one of them all. Is there a book that specializes on Monads? A Haskell-Monad book? Günther