Sometimes I realize just how little history I actually know, even though I do think I have a decent broad strokes overview but, wow, this was absolutely fascinating and Tuchman's investigation into all the different things happening was just really cool.
The research and narrative structure made it work as a book rather than a textbook; I think I would have felt differently about it if I was reading for research rather than just to know more about everything. And I do finally understand what was going on with the whole "We've had one pope, yes! How about second pope?" situation.