Intro: This is a great product for anyone who wants to run a Stalker game based off the original novel (Roadside Picnic) and movie (Stalker, 1979). If you want something that mimics the computer games (the S.T.A.L.K.E.R. game series), this is not for you.
Content: It's almost entirely setting and GM information, with only a very small portion devoted to rules - and if you don't like the rules (a unique diceless system that relies heavily on freeform storytelling and the GM's interpretation), it's very little work to strip them out and insert your favourite system. The book is split into two parts - a "Player's Book" and a "Game Master's Book", which contains information for each of those. In addition to the general setting of the world, two of the world's Zones and their Borderlands are detailed, along with plenty of information to generate anomalies and artifacts if the GM's imagination is stuck. Interior art is mostly B&W and fairly basic, but has a kind of 'noir/crime' feel to it that I liked. As an English translation of a Finnish work, any language errors are almost unnoticable. The download includes the rulebook, plus a separate character sheet .pdf.
Criticism: I am a tiny bit disappointed that it didn't come with more original 'pre-generated' anomalies, artifacts, inorganisms and mutants (most of the ones detailed are present in the book or movie), but it does encourage a GM to make them ahead of time and memorable. I would also have liked an example "rookie mission", a detailed scenario of a particular raid into a Zone that starting characters could be expected to complete. The system does not include much on character advancement, more or less being "when he is taught or practices a new ability for a while, add it to his sheet". The main improvement I could suggest is to offer separately or include with the download package the "Player's Book" as a separate .pdf file, so that it can be shown to players without also having all the Game Master's Book info as well. I am a little confused as to the purpose of Ability scores in the system, which don't seem to mean anything except as hit points.
Verdict: A great sourcebook for anyone wanting to run a mostly-freeform game in a Roadside Picnic/Stalker-inspired setting. First and foremost a setting guide, where a little bit of work could make this compatible with virtually any rule set. It has a ton of background info, and most of my critisisms boil down to wanting more detail. The rule system seems a little clunky for what is essentially a freeform system, but it's easy to gut it and stick new rules in.