Last but not least is this small and abridged guidebook from Sebastian Schwertner, written for extreme climbers. This guidebook details, in English, the places you'll want to go in the northern Frankenjura if you warm up on 5.11. It is definitely written for the visiting climber and is therefore probably the best guidebook for the area for those of you thinking of coming for a visit. If you're interested in buying it beforehand you can get it at the given link, or I'll sell you my copy for 5 and you can pick it up from me when you get here.
To clarify, the book provides directions and descriptions for hard crags, which also often contain easier routes. So it's not exclusively for hard climbs.