The film, which is the last one that Heath Ledger made before he died in New York, is a Batman movie and sees Batman (Christian Bale) do battle with The Joker (Ledger), along with Commissioner Gordon (Gary Oldman) and Harvey Dent (Aaron Eckhart), the local DA.
The film was pretty good, in a dark, grim sort of a way. I thought they dragged out the ending too long (had they stopped it before the damage was done to the Police HQ I'd've been more than happy), and the twist in the tail was a little disappointing, but all in all it was still pretty good.
Incidentally most reviews've been raving about Ledger's performance in the film. It was good, but I wasn't stunned by it. It reminds me of the "Sheriff of Nottingham" in the Kevin Costner film "Robin Hood: Price of Thieves." Alan Rickman (the Sheriff) stole every scene he was in, but it was still a "comic book baddie performance" and I'm not sure he was entirely worthy of all the praise he got.