In reply to purplemonkeyelephant:
There's no one book to cover all of the Peak grit, but the Rockfax Eastern Grit covers most of the grit crags you're likely to go to from Edale. (Not the ones up on Kinder though, they're in Western Grit.)
The latest BMC definitive guides are excellent, but probably not worth it unless you're planning to spend a fair bit of time in the Peak.
(You'd be wanting 3 of them to cover the same area as Eastern Grit.)