In the first episode we are introduced to John Constantine (Matt Ryan), who looks exactly like how he does in the comic, which is a plus, a far better casting choice than Keanu Reeves (who was in the CONSTANTINE movie). It's established that he's involved in the supernatural--and that something horrible in his past has destined him to hell, which is brought up by "Manny" a weird-eyed angel (Harrold Perrineau of LOST). In the second episode potential love-interest Zed is introduced, in a story which concerns a local mining community in Pennsylvania plagued with underground creatures. Zed has been drawing pictures of Constantine for months and when she runs into him sticks by his side. In the third episode, there are lots of Doctor Who references, from a magical safe house looking larger on the inside, to Constantine showing a blank card which can turn into any sort of ID the viewer needs to see.
This is a great adaptation of the comic book series. The only way it could be improved is to have it take place in England, not the U.S, which sort of diminishes it a bit. Also, because of shows with similar themes, namely SUPERNATURAL, have been on television for a decade, this show doesn't seem all that original, particularly with the whole Angel/Demon situation. This is too bad for the show--but it is ten years too late.