Let's start by the fact that it has a demo (+1), Always better trying a demo than buying a game and feel like being cheated.
It is an open empty world. Meaning that you can run a lot, everywhere, and find nothing. just plain fields.
Run, or drive.
You got a car to enhance, by buying new engines, protective gear (SPIKES) And Nitro, helpful if you've got one of these moments where you want to jump from high cliffs. Careful tho, as your car is damageable and can lose parts of its body.
Driving is quite enjoyable and responsive.
You got 5 weapons (One of them is a baseball bat which sends zombie flying scoring home runs).
You simply are an average hero who's going to save the world from a zombie invasion. Nothing more, nothing less.
It's an average game, with a debatable humor (I found it funny, tho.), go-there-and-do-this-then-come-back mission type,
a race, an entire city to free from mafia (Zombie).
The soundtrack is pretty good, it's jut a bit limited and you'll end up hearing the same song three times in a row, too.
Graphics aren't the best, but cities and other places are, in my opinion, detailed. By detailed I mean that there are a lot of particulars that add a bit more dynanism and entertain the eye. I often found myself moving the camera around, trying to find something odd, unexpected.
After all I still recommend it: calling it the worst game ever is overly exaggerated, although there aren't 5 bosses and the story isn't exactly well written. It's just an average game, enjoyable if you don't expect that every game you own is a GOTY or received a score of 90 / 100.
The only real advice I can give is to not buy it on full price, wait for at least 50% discount.