In reply to sabostar:
Those two books above are probably the best resources, but here are two older ones you might find on the cheap:
- Arran, Arrochar, and the Southern Highlands
- Classic Mountain Scrambles in Scotland
I got both either on UKC or in charity bookshops, whereas I paid full price for new versions of the Highland Scrambles South and Scotland's Mountain Ridges.
In terms of route recommendations, here are some classics I regularly visit:
- Arroachar / Cobbler: Climb southeast ridge (Mod) , descent the original route (Mod), climb the arete (Diff)
- Glen Coe / Buachaille Etive Mor: Curved Ridge (Grade-3/Mod)
- Glen Coe: Aonach Eagach (Grade-2)
Plenty more obscure things out there if you look around though! Arran is also worth the trip as it has miles of ridges with anything from Grade-1 up to Diff.