In reply to Alistair:
It depends on the season and activities but these are the topos I use;
sort Lang titel ISBN
topo FR Cascades de glace du mont Blanc au Léman (tome 1) 2952188157
topo FR Cascades de glace du mont Blanc au Léman (tome 2) 2952188165
topo FR Cascades Oisans aux 6 vallées 2950986838
topo DE Mont Blanc Gruppe 3763324143
topo DE Mont Blanc Gruppe 3763334092
topo FR Snow mixed and Ice volume 1 2952188122
topo FR Snow mixed and Ice volume 2 2952188149
topo EN The 4000m peaks of the alps 97809005233663
topo EN mont blanc 100 finest 9781906148645
topo DE 4000er 9783765437960
I think the mont blanc 100 finest one is the best guidebook ever! All sorts of climbing from easy to extremely hard with everything in between.
also camptocamp.org and chamonixtopo.com have detailed route descriptions on a broad scale of routes!