I'm a fan of the co-op horde shooters like this, vermintide, and of course left for dead so take that into account when reading my opinion. World War Z is quick and basic which I like because I work and have a two year old son so my game time is fairly limited. I love being able to jump in, play a level and log off but admittedly this game makes logging off tough because the quick levels are so much fun. You start a level at point A needing to go to point B with a few uninspired objectives along the way but there are also hundreds upon hundreds of zeds trying to make sure you never make it to B. Co-op is key; stick together, share resources, protect eachother instead of one's own interests and not only are you gonna get to point but you're gonna have fun doing it. Different classes of survivors to level up and experiment with but on the lower difficulties classes don't make a big difference. Also each weapon has its own leveling so no matter how short your session you're going to be moving forward so long as you finish your given scenario.