Why don't you own this? Go out and buy it, you!
Even if the gameplay is a bit different, this is still very much a Fallout game. Bethesda perfectly captures Fallout's signature "Atomic age gone too far" aesthetic, and the black humor and cheeky Vault Boy illustrations are all present and accounted for.
Overall, this is an excellent RPG-- one of the best. It's hard for me to do it justice in a simple review since there's so much that is good about this game, but suffice to say, if you want an awesome game that combines the RPG genre with aspects of a First Person Shooter, do yourself a favor and buy this. Believe the hype, Fallout 3 is the game to beat.