In reply to Ian Archer:
I think there is a use for both. Right now for multi-pitch I end up taking photos of the guide book on my phone so I can check the guide at the belay stance.
It's a _real_ shame that the UK Climbing guys haven't made a decent app for this site yet. All it needs is to store offline all the information for a crag (descriptions, comments and pictures) and they would be onto a winner. You still want the guide book but all comments and grade votes are really useful before you start a climb.
Instead they have decided to sell guides, but there coverage is really bad as they haven't done many and in any case half the crags are covered by Climbers Club not Rockfax.