Finished Metro 2033.
I though I could write a bit of my thoughts, I know plenty of people here read it.
The book definitely has its moments, though it has its downs too. Generally, what is easily noticeable is that the writing improves over time, this being an Internet novel originally, and as the author himself states, a lot of the improvement comes from the readers who gave constructive criticism at time where it was needed - mainly regarding the technical bits (e.g. metro construction and its characteristics, military tech and weapons etc.). Only thing where it somewhat "fails" when regarding this stuff is science - a lot of stuff is just left to the allmighty radiation to mutate, alter, twist and corrupt - which I personally find somewhat annoying. Anyway, this isn't really the down factor.
The setting is pretty awesome and quite original, and the characters and story set in it are pretty good too. It suffers from some seen-before moments, especially in the beginning of the novel, where it is a standard bildungsroman - it stays like that until the end, but with a lot of philosophy involved. Whereas in itself it isn't something new, it is cleverly used.
The story itself is pretty dynamic with a lot of characters (again, it was an Internet novel), and though certain chapters can be marked boring (at least to some extent), it is all combined well in the pretty powerful ending.
Personally, I recommend the book. It's not the best on the shelves, definitely, but it is very good.
Also, as a note for all those who played the game but haven't read the book - I've never played the game, but I've seen the trailer and read few reviews. From the looks of it, it barely has anything to do with the book, and "breaks" the story and elements of the setting in favor of action...it's a shooter, after all.
I'm not saying it's a bad game, but you should forget all about it and read the book.