Emperor Julian, Constantine’s nephew, rejects Christianity, which in posterity will earn him the epithet The Apostate, but turns out to be a pretty good guy, at least as Roman emperors go, which is not saying much.
Although he despises Christianity and wants to re-institute Paganism throughout the empire, he issues an edict that all Roman citizens can practice the religion of their choice, while keeping most Christians out of positions of official authority. His harshest measure against Christians is forbidding them to kill each other for heresy, which by the time of Julian has become one of the most enthusiastic enterprises of the various Christian sects and which they will cheerfully resume after a Christian emperor is restored to the throne.
Source — Edward Gibbon.
It might be superfluous after reading Gibbon, but I really enjoyed this Great Courses series: http://www.thegreatcourses.com/courses/fall-of-the-pagans-and-the-origins-of-medieval-christianity.html
Gibbon is no longer the last word on this subject, of course, and it would be interesting to compare his analysis to the analysis of modern scholars, but it’s hard to imagine having the energy for that after getting through Gibbon. After 800 dense pages I’m only a third of the way in!
I have the 3-volume Womersley set and a 1,200-page Modern Library abridgment. I doubt I’ll ever have the stamina for the complete thing but one day I’ll tackle the single volume.
It’s surprisingly entertaining.