It's alright, but playing it after reading the book makes it look like crap. It's too bright alright, I expected the metro to be pitch black, maybe with even using a new game mechanic noone else tried so far: navigating through levels where you only HEAR and not SEE. Anyway, this is probably godhard to do and it's just a silly game idea my brain farted out when reading the book. Still, navigatin through pitch black tunnels with a single flashlight or in cases bigger light sources would have made a better atmosphere than a series of tunnels lighted with atmospheric green Halloween stagelights.
Point is, yeah it's alright but I could not imagine how they'll make the book into a videogame. The answer is: completely rewrite it, which is bullshit. Yeah, main characters are there (some are renamed though; are they afraid of russian names or what?), some story elements are untouched and all, but overall it's just a bleak reminder of the book. Why couldn't they make a game based in that universe and then maybe make it have a close connection to the book? Why not have a sequel to the book and the game (which is confirmed), and have them lead 2 parallel stories, intertwining and/or eventually merging? I'm also not nitpicking here; for Christ's sake you go on the surface before meeting Khan (happened WAY far in the book and Khan was nowhere then), with a guy who, without spoiling anything, just should't be there, and in broad daylight. Artyom almost dies because of daylight in the book; not only is it lethal, it can blind anyone too.
The most inexcusable thing it has is spoiling the very awesome Outer Limits-esque ending of the book, which makes me ironically wish if they altered that too to a more hollywoodish ending. This is only because the book, as awesome it may be, was a lot unfocused. I rarely use that word, but here I still didn't know where the plot was heading before the last chapter. Surely, the surprising ending all fixed that but it hardly stands as an excuse for it. But try reading the book now, where you know what happens in the end. That one huge redeeming factor to a decent book is spoiled, making it only a decent one instead of a very good one. Man I'm glad I've read the book first.
Anyway, the game part of the game is alright, I didn't care too much about the stealth as at least it doesn't require you to do it, only a suggested way with alternative solutions. The combat is all good, and I like the atmosphere despite bearing no similarities to what I imagined from the book. It's an above average shooter, but I won't recommend it for anyone who wants to read the book. Go get that instead, you should play the game after FINISHING it. Other than that, yeah it's... good.