There is a working copy in the Manx museum (originals are usually very expensive - several hundred pounds) - there is a reprint of the Atlas done by Shearwater press but it didn't sell - Mannin Collections has bound a few and sells them at about £200 IIRC. The fam hist library at Peel has a copy I think.
(for those unfamiliar with original layout see http://www.isle-of-man.com/manxnotebook/gazateer/woods/sn.htm - I have scanned in all parishes but most are still on my back burner to correct - maybe I should do so !)
To be honest I havn't found it that useful - Thwaites directory of 1863 gives addresses and tenants, ownership is generally less useful unless you are tracing property for which I'm afraid the maps are essential though these are more useful read in conjuction with the almost contempory 25inch OS plans (I have about 60% of these) - the maps are larger than A3 and the copies dont scan well as the leterring is very small (and require an enormous storage) - I guess I should experiment with digital camera and the originals (which are coloured - almost essential) but definitely too big to go on-line - during the many days spent at Manx Museum I have seen few people actually use them - their main use is to go from a geographic position to a tithe plan and name - the map is essential here