I didn't have high expectations for Zombie Driver HD, but it's suprisingly good fun mowing down zombies in your car! My fav mode to play is Slaughter (survival) where the zombies keep coming which also has an online scoreboard to challenge your friends. Story mode is repetitive and gets pretty boring; there is a lot of content for the money though! Blood Racing is OK but most enjoyable once you get a good ride. Decent array of weaponry & cars to choose from which are all upgradable (off course :p).http://steamcommunity.com/sharedfiles/filedetails/?id=188479432
I created a section in the guide above which has a quick list of what you get in the DLCs. Also covers things like the vehicles, game modes etc which might be helpful if you still want to get a better feel for the game.
Definitely good value, a few weak points short of a classic but overall a solid, fun game!
Worth checking out if you like top-down racing games.