In reply to SFrancis:
It would be an awful lot of work to compile it as well. You've got to imagine that quite a few climbs that have been done since ER would need to go in (The Rathlin Effect, Meshuga, Once Upon a Time in the South West, Dalriada, Skye Wall, Divided Years, Longhope Direct, The Big Issue, Welcome to the Cruel World, etc. etc. etc). TBH, there's a coffee table book waiting to be done for the level above 'Extreme Rock'. I'd imagine the hardest part would be coming up with a suitable name. Hard Extreme Rock? Hard Very Extreme Rock? Surely there has to be enough good photos of those cutting edge routes as well; I imagine most had someone on an ab rope snapping away.
Having read some of Caff's blog posts on the routes (especially the write up of Master's Wall), I'd love to see a book of his experiences on those ER routes. I'm sure he's at least been approached on it already.