I find this to be very sad news. I am currently marathoning the show on Hulu. I love the show enough to watch it again, for the third time. I love John's amoral nature, he was the largest inspiration for the show Supernatural. He's willing to do bad things for a good reason. John uses magic and demons to get what he wants. You have the Angel, Manny, who might not be so holy. And Zed, who gets visions and is running away from a past we are just beginning to guess at. There's also the loyal Chas who just won't die. The whole cast is quite compelling.

Constantine had done several faithful adaptations of the comic book stories, making changes where necessary, but faithful all the same. The best, and most chilling, was the finale. That story gives me goosebumps in both forms. The show also laid the ground work to bring in fan favorite characters from DC Comics, such as The Spectre and Dr. Fate. The show had already introduced Jim Corrigan and alluded to his eventual death and tenure as the host of the supernatural entity The Spectre.
I would encourage everyone to check out Constantine on Hulu, all of the episodes are up, but only for a limited time. The final five episodes are up on the NBC site as well. I know we often lose the shows we love, so this is yet another time that I will be campaigning for people to watch a show so it doesn't get cancelled. This is just another in a long line of great show to die before their time.