Preacher was a DC/Vertigo series of graphic novels by Garth Ennis and Steve Dillon that ended in 2000. I didn't read the whole run, but I read pieces and it was entertaining. On the graphic novel scale, it was a bit on the weird side - a preacher gets the power to command people (they have to obey him), and he tries to use that power for good. And his best friend is a 119 year old Irish vampire. That's not too strange as graphic novels go. But on a TV scale ... it's batshit crazy. And I was dying to see it. The places it goes with regard to religion (which I can't discuss without spoilers) - I'm completely astounded this was made in the U.S. Fine, it's AMC - it's still made in the U.S., a country that doesn't take well to the kind of sacrilegious concepts this is messing with.
You've got the basic idea: Dominic Cooper is Preacher, aka Jesse Custer. Ruth Negga is his dedicated and exceptionally passionate (ex-?)girlfriend, and Joseph Gilgun is Cassidy the vampire. Cooper is British, but doing a surprisingly decent American accent. Not perfect, but very good. The acting is good throughout. It's true to the graphic novel, complete with all the craziest bits and the significantly uneven plotting - but uneven or not, it's vastly entertaining and I've really been enjoying it. I look forward to the second season.