I was really excited about this show, but it ended up being pretty horrible. I read a few of the comics, but not many. I was a bigger fan of the Keanu Reeves movie version. Constantine is supposed to be a pretty dark and serious story and has lots of angel and demon based lore. The Keanu Reeves movie got a lot of that stuff right, except Keanu Reeves didn't have the right "look".
This show though is almost opposite. The main character is goofy and lighthearted. The atmosphere is comical almost. The lore is barely there.
The show will be cancelled after 1 season. There was a petition started by fans to save the show, but even that flopped haha.