Overall the game isn't too bad but if your expecting another Resident Evil 4 or 5 then look elsewhere.
Gameplay - To be honest, the game is pretty hard even on the easiest difficulty setting. If your one of those people that likes to charge through enemies and do a bit of CQC then your gonna constantly get killed. The enemies have more health than you would expect. The controls are very easy to get used to and can also be pretty annoying at times. To put your back against a wall, you simply just walk/run into it and your character automatically does it but not everything you can do this on, like sometimes when you are taking fire, you might try taking cover behind an object only to see your character running into it instead then getting killed because that object apparently couldn't be used as cover. Also, you and your teammates can get infected by zombies randomly if you get attacked by one. To cure yourself or your teammate, you have to find a anti-virus spray then use it. If you fail then you will become a zombie and the game will end. If your teammates become one though, you can just kill them then revive them afterwards and they will be fine. There are also some cool melee moves you can do as well like pressing B then A will instantly kill the enemy your near to (except a boss of course) or B and Y.
Campaign - There are six characters to choose from. Personally, I prefer Spectre as he can detect all usable items around each level which helps if you need health, vials or ammo. I think the major problem with the Campaign is that there is no local Co op play and if you choose to play Single Player then you will most likely have a frustrating time with the teammate AI especially if your playing on a high difficulty level. While you're firing your weapon, teammates like to walk in front of your gun and you will instantly kill them with a headshot. Luckily though, you can revive them as many times as you like. Another problem though is that they cannot revive each other. If you choose to play the Campaign online instead, your going to have a terrible time at finding people. The matchmaking system is poorly done, you can't like display a list of which games to join, the game just basically puts you into any game whether it's a game in a lobby or a game in progress. I remember when this first came out, I had to wait 20 minutes for one player to join. Without spoiling anything, I thought the story was good but it could have been a lot better. If you don't have any friends to play it with, I wouldn't recommend getting the game.
Versus - The modes here are Team Attack which is basically Team Deathmatch, Biohazard has you and your teammates running around the map to pick up vials to return like a Capture the Flag mode, Heroes has you playing as previous Resident Evil series characters and is probably the most fun mode and in Survivor you gotta hold out until a helicopter comes to pick you up. Versus mode has a lot of connection issues and glitches but is actually quite fun, definitely worth a go.
Other - The achievements are quite challenging, some require a lot of Versus mode play and ones for Campaign like getting an S rank on all levels will need a lot of practice. The DLC for the game has you playing as a Spec Ops team (good guys) and has you running through the same Campaign missions except backwards lol Has a few new areas though and Versus maps. There is also a Nemesis mode which I have yet to try. The rest of the DLC are weapons which aren't anything to jump up and down about.
So yeah if you want another shooter with zombies or if you liked the Army of Two games, check this out. If you want another Resident Evil game then your best waiting for Resident Evil 6