Hitman has always been one of those books that's right on the edge for me. It's just good enough that I keep picking up the trades when I find them (cheap or in a swap). Ennis (writer) does a decent job of characterization of the roguish Tommy (the titular hitman) and his buddy/partner Nat. Their friendship and banter is mostly what makes the book; but it's also Ennis' hatred of the superhero genre. He loves to poke a finger in its eye. I've never cared much for McCrea's artwork, it's too knobby for me, but for some reason the coloring and overall momentum of the story made it less of an issue for me. Ace of Killers features Tommy teaming up with the Demon and Catwoman to take down a different demon. It also features a budding love affair for Tommy. Somehow it all comes together to make it probably my favorite of the Hitman trades that I've read.