In reply to ned taylor:
If you don't get up to Scotland much then I'd suggest the SMC Scottish Winter Climbs along with its summer stablemate as covering pretty well all of the classics you are likely to be wanting to do. (There's the two guides by Gary Latter for summer as well)
Of course if there's a queue on your chosen route then having the definitive guide helps a bit more with alternatives as waiting around for two or three parties in winter is no fun (nor is climbing below them!)