I noticed this was streamable from Netflix, and with Mrs. Salad out of the house for the evening, why not? I was shocked to discover that I'd watched the original Sin City back in 2005; was it really that long ago?
My comment at the time: "Not recommended for anyone under 45, or over 55." Now I'm well over that suggested age limit.
In any case: this movie connected to the original through some of the characters. There's Marv (Mickey Rourke); Nancy (Jessica Alba); Gail (Rosario Dawson); Dwight (Josh Brolin here, was Clive Owen previously); the evil Senator Roark (Powers Boothe). And Hartigan (Bruce Willis). There are multiple subplots revolving around new characters: cocky gambler Johnny (Joseph Gordon-Levitt) and manipulative Ava (Eva Green, also providing nudity).
It's all sordid and violent. Most people seem to think it's not as good as the original; it also seems to not be as original as the original.