Upvote:0
I saw this book at a used book store ans almost bought it once purely out of curiosity. If you're American it probably will give you a pretty good understanding of the multitudinous denominations. It's fairly amazing that such a thing can even exist.
A helpful resource for clergy, laity, journalists, and researchers, this authoritative guidebook to U.S. religions is grouped in family categories of Abrahamic religions, arranged chronologically: Judaism, Christianity, and Islam. The information for each group within these families has been provided by the religious organizations themselves and focuses on the denominations' doctrines, statistics, and histories.
Handbook of Denominations - Amazon Blurb
I think the older editions didnt have Islam and Judaism in there, but I could be mistaken (my last recollection of the book was spending half an hour reading it in a bookstore 15 years ago)
Upvote:2
For ease of access and breadth of scope, it would be hard to go past Wikipedia. Perhaps you should start with either their article on Protestantism or the one on Christian denominations and then start chasing links from there.