Why spend unnecessary hours hacking your way through a bookish biography of Constantine, the first emperor of Christendom, when you can pick up the essentials in under four and a half toe-tapping minutes. Some months ago I read Paul Stephenson's Constantine: Unconquered Emperor, Christian Victor. To think, all I really needed was the good services of YouTube! "Oh," as Dr. Smith was wont to say on Lost in Space, "the pain, the pain!"
Okay, so there's not much critical content, but then again, the Eastern church turned this pustule into a saint so, hey, who cares? And once you've absorbed the info on Con, you could even try your luck with Martin Luther.