If I had to sum the whole thing up, I'd say it's "a pretty good journey to get to a really, really, really bad destination." The ride to the ending is pretty entertaining and makes you wonder exactly what's going on. Then you actually get to the ending, and not only does it make absolutely no sense, and not only does it feel like it was made up on the spot, but several things in the story make much less sense in hindsight than they did before.

The ending largely renders everything that happens in the story pointless, pointless enough that if I'd known what the ending was going in, I wouldn't have started reading it.