Gameplay is good, plot not so good.
The plot in question is pretty thin and far between, but when it pops up it's totally unbelievable, and the thug sequences it inspires are by far the hardest and least enjoyable segments of the game, though thankfully they're few.
To get my other complaints out of the way right off the bat: the game also fails to make strong use of mechanics it introduces. You've got a thirst meter, but if you keep even one medium bottle of water on you you're pretty much never at any real risk of running out. You can assemble items out of other items, but there's not even one place in the entire game that you need to do this. In fact, outside of a few critical puzzle items and the aforementioned water bottle, there's really not many items you need to use at all. Oh, and the camera can be a bit annoying: there's a button that shifts the camera behind your character's back, but that doesn't work in all areas, and you can shift to first person and look around that way, but bizarrely enough it starts out pointing the way the camera was pointing, not the way your character was. Finally, I wish they had allocated a button to jump on its own. As it stands, you have to run and you will automatically jump at the end of the surface you are running on, in whichever direction you were facing. This can occasionally cause problems.
On the other hand, the central scenario is very well rendered. The manifold dangers you encounter are consistently thrilling (if not always completely believable). Your next course of action is usually intuitive. The scenery is, if not all that exotic in basic components, certainly spectacular in the ways those components are destroyed and collapsed, particularly toward the end of the game. As you progress in the city, the time of day shifts accordingly, with appropriate changes in level and color of light, weather, etc. Too, your character and the others you travel with progressively become more banged up, ripped up, and dirty of clothing as they travel. By the end Keith's jeans will be fit only for the garbage heap.
Instadeath is rife, but absolutely appropriate (how many buildings falling on you could *you* survive?) and rarely much of a setback. All in all, it's as close to the aftermath of an earthquake *I* ever want to come. Quite the experience, and at the current bargain basement price of 9 or 10 dollars used, worth seeking out.