For those who don't know, Constantine is based on the very popular DC/Vertigo Comics series Hellblazer, which originally ran from 1988 until 2013. The comic starred John Constantine, who was a magic user and detective who handled occult related incidents. Fun fact: Constantine's physical appearance in the comics is based on that of Sting and apparently he was originally created by Alan Moore because Stephen R. Bissette and John Totleben wanted to draw Sting in an comic.
I have to wonder, though, if Constantine will even survive a season. It seems a bit outside of what NBC or any of the networks normally do, but then again, so is Hannibal, Sleepy Hollow, and Once Upon A Time. Who knows, maybe broadcast networks are finally expanding their horizons beyond what their comfort zone in response to Netflix and internet-based entertainment.
Bravo for actually casting a Brit to play Constantine, unlike a certain movie that shall go unnamed.