There is a new book out on Marco Siffredi written by his friend, the journalist Antoine Chandellier. Although it is written in French it is a reasonably easy read and there are 300 photographs. One to check out if you visit a bookstore in a French resort this season.
As Chandellier once told Marco "in any case, you don't even like snow Cocco, up there you track it without stopping, there isn't a virgin slope left".
I've posted a longer review here:
Marco Siffredi - the footsteps of an Angel