[image from the Rocktar GTA site]
The Rockstar site has plenty of official info to get started with with images, characters and such. The environments are full of detail, character and dynamics - will be great to get this on the PC (Windows - well going by the previous versions we should have it this year).
[screenshots of GTA4 from the Rockstar site]
But it is video that shows off this game best - lets let youtube do the talking - first one of several trailers, then the IGN review:
Over on CGSociety, Tom Bramwell has a nice interview with the art director Aaron Garbut where they cover the design of the characters and the incredible Liberty City. There is a little bit on teh Euphoria engine (from ILM Star Wars fame) - awesome. Here is a little quote from Aaron on the lighting setup:
I think the lighting system in general is pretty amazing. There are no hard limitations on the number of active dynamic lights around the player. The real-time shadows are working across every object and surface in the game with everything self-shadowing and casting onto everything else, there's ambient occlusion and emissive lighting on top of that. And then your standard next-gen shenanigans - light shafts, bloom, depth of field and motion blur, and of course it goes without saying everything's rendered with HDR.
[some more images from the CGS article on GTA4]
Digital Urban have had a look at the engine a little (previous incarnations that is). I will be keen to see if getting content into the new engine (with all its juicy bits) is a viable task as well.