It's basically the newest True Crime game.. for whatever reasons the developers abandoned the name and went with Sleeping Dogs.
That's a very rough overview, i'm sure someone here could clear it up for us
The only issue I have with the game is the combat. I haven't played it, but from what I see/hear it's like 80% melee combat, which, I don't know... a 20 hour game or so with mostly just punching dudes in an open world game just seems..odd.
Other than that, the game looks pretty great, I'll probably Gamefly it next.