the 'best' month is really gravy because even a mediocre month in the Rockies can be awesome by the standards of other destinations. Last year I spent 1 1/2 weeks there in mid-november, during a chinook, and still got in 7 great days of climbing, each in a different area. Long days are nice - but so's a good headlamp (or two).
As far as the guidbooks go - Caveman has the link for the water ice guide, but if Mixed Climbing is your deal you need to get the Sean Isaac guide too. At least rmbooks sells guides for a reasonable price though.