Gamespot has posted their preview of Fallout 3. They sum it up nicely in one paragraph:
First, here are some key basics about Fallout 3. Yes, it's a
first-person game, but it also has a third-person camera if you like to
play that way, and the camera can be moved so that it almost mimics the
perspective of the original Fallout games. No, it's not a pure action
shooter, though it can be played like a shooter in some ways, if you
want. However, the game does rely on role-playing statistics to
determine whether you hit or miss. More intriguingly, you can pause the
combat at any time and target specific parts of an enemy's body, just
like you could in the original Fallout games. And, yes, it's very much
a role-playing game with hundreds of quests. While it only has a few
hundred characters as opposed to the 1,500 in Oblivion, each of the
characters in Fallout 3 will have his or her or its own distinct
identity and dialogue. But we'll cover all of this in a bit.
As for the setting, we know it's in the DC area, but:
Fallout 3 is set approximately 30 years after the events in Fallout 2, though knowledge of the first two games is not required.
And we finally find out what the deal is with Paradise Falls:
When you reach the outside world, you'll find yourself in the blasted
wasteland in and around Washington D.C., a departure from the American
West seen in the first two games. This is an area teeming with wild
creatures and rival factions, such as the Brotherhood of Steel, which
defends the remnants the capital; the Slavers who occupy Paradise
Falls, a converted strip mall; and the super mutants, tough-as-nails
humanoids looking to take over
[Y]ou can create your own weapons from various [spare] parts.
Go here to read the rest of of it.