In reply to dan wisey:
I was there at the end of March this year. Based at Refugio Campo Base http://www.campobaseacceglio.it/en/ at the end of the (open in winter) road near Chiappera. A very good place to stay if want somewhere not too fancy, €46 a night half board. Very good food, the staff are very friendly, knowledgeable about current conditions and suggestions for tours, plenty of tours that you can do from there, and a lot more a bit further down the valley.
The guidebook in German or Italian is very good, its for sale in many places in the valley, easy to use with the map (which may be sufficient as already mentioned). A really good location, not too busy midweek, most of the other skiers seemed to be German speakers.
Worth noting that last winter was very good in terms of snow cover, in many winters that may not be the case, but usually plenty to do.
There are a few bivouac huts around that are interesting and sometimes well equipped, as well as the odd winter room in huts (including across the French border). An example of a tour we did: https://www.strava.com/activities/1474718783
Hope that helps.