Hardiness Zones are stated for each species in my copy of this excellent book, with zone maps of North America & Europe toward the back of the book (tho the Europe zone temps do not seem to agree with those at http://www.uk.gardenweb.com/forums/zones/hze.html).
This is a very helpful & extensive listing, but many additional species are at least described (if not offered for sale) on various current web sites.
I strongly enjoyed the author's wit, notably directed toward the bulbiliferous species ("villains" "self-perpetuating thug[s]" "pestilential weed[s]."
This is the definitive book for those interested in ornamental onions. The book covers the vast majority of the species currently in cultivation, giving descriptions of the plant, synonym names and cultural hints. There are plenty of pictures to go along with the descriptions. There is even a chapter on recipes that use ornamnetal onions! My only disappointment is the fact that hardiness zones are not given for the various species.