I've played a good few hours or this now. I kind of think of it as Left 4 Dead meets Borderlands. It reminds me of both, L4D due to the fighting though hordes of zombies, which you seem to come across bigger and nastier ones as the game progresses, and Borderlands due to the RPG type element, though I guess you could use any RPG game to explain that side of things.
I played like I said a few hours, you start off on the coast mostly working between a lighthouse and a lifeguard tower, but I have a tendency to get distracted and not follow the storyline in open world type games as I collect every quest available and go do them all at once before I even attempt the story. So after many side quests and many zombies slain just for the hell of it, I finally get on with the story. You start off helping the guys at the Lighthouse and Lifeguard Tower gathering supplies and such. Because you are on the coast and only have a few bars and occasional shop to ransack the supplies you do get don't last very long. So you are asked to further inland to the city to stock up on as much as you can fit in your armoured van (which you get a little earlier after finding a mechanic and saving his daughter) which looks pretty kick ass if I do say so myself. Anyway you head into town, end up having to help more folk in different scenarios. Along you go killing zombies with whatever weapons you can find, which leads me to my next point.
The weapon build system, you get random work benches round the island where you can repair, upgrade or create new weapons. It's a lot like the Dead Rising system. I'm currently using an electrified machete which seems to work quite well at killing most things, just need a knife of your choice, some duct tape, a couple batteries, some wire and you'll be frying zombies in no time. Though you do have to make new weapons every few levels or so as they lose effectiveness when you go up against higher level zombies, so make sure you weapons are round about the same level as you are, you don't start off with any weapon mods but you get more over time though quests or just random looting (which is a must if you want to upgrade).
You also level up after getting so much xp from killing or questing, giving you a skill point to upgrade your special attack, your weapon abilities or survival skills. Each of these very depending on which character you choose to play at the start of your game. I chose Xian, who is an undercover cop that is good with blades, which is why I primarily use machetes, I have 4-5 in my weapons list. But the other characters have different stats, be it more health, quicker attacks and different weapon specialities. Sam B is a stereotypical rapper that specializes in using blunt force (eg hammers, pipes and what not). Logan is an egotistical former pro-football player with a fondness for throwing things, and last but not least is Purna a former police officer turned bodyguard that likes to shoot. It is quite a n addictive little games, I've seen myself just about to call it quits, then thinking I'll just do one more quest then I'll turn the game off for a while, next thing I know its 2 hours later.
I haven't played coop yet, but will do some point down the line, from what I have heard about it though is quite good with you can drop in and out with friends or randoms whenever you like, and when you do join you don't have to stay together and can wander off from each other for a while if you have different objectives. So you can go do a quest your team mate has already done while they continue doing whatever they are doing. I reckon I will play through the game again with a different character once I have finished this run though. I'm definitely not bored with it yet. Whether I will get bored easier on a second play through time will only tell. It seems like a good little game, and I believe some dlc has been already announced for it. Hopefully they will keep updating the game so folk won't be getting bored with the content any time soon.
I would say if you like killing zombies and you like RPG aspects in games along with some pretty funky weapon upgrades, you should definitely give this game a shot.