This thread deals with how the MG songs are played.
There haven't been any official tab books for MG's music, but there are plenty of tabs available online (Ultimate Guitar Archive is a good source). That being said there are a few favourites that are incorrect or missing altogether.
Are there any MG songs you'd like to learn to play that you can't find tabs for?
I'd like to learn his solo version of 'while we were hunting rabbits', but I can't seem to get the chords, or even the rhythym, does anyone have any insight?