It's pretty good, basically...a corporation is pretty much allowing people to "log in" to their virtual community, which feels extremely real. One of the prerequisites of entering the community "Union City" is that you're implanted with a cerebral chip in your brain.
This chip, depending on your access clearance, will allow you explore/live-in certain parts of this virtual world. Problem is, the chip in your brain is at the mercy of the corporation. And we all know how power corrupts.
The storyline is just enough to keep you playing, and I love how you get to explore the world and different houses along your journey. Leveling up is pretty cool, because you can decide to level up your combat tree if you want to go Commando style and just shoot up the zombies...or you can level up your stealth tree if you want to sneakily kill zombies (my preferred choice).