In reply to Martin Bennett:
Paul Nunn's guide is fundamentally flawed as a guidebook: it's very hard to use and the grades are all over the place. It is a terrible choice for someone new to the area. On Peak Rock in contrast is still brilliant fun and very usable (especially the first edition, with the wonderful crag selector in the appendix) but probably a bit old in style for those used to photo topos and quite large for some for crag use (but it's essential for any guidebook collector for a home library).
If the OP wants just one modern volume then the VG Peak District: climbing guide is the best for lower grade climbers or there is POD's topo guide mentioned above or wait a few months for the BMC Wired grit guide or Graham Hoey's selected grit guide (bloody busses all coming at once).
Post edited at 12:28