A group of stalkers, for the first time, reaches the very heart of the Zone-the Chernobyl Nuclear Power Plant-and triggers a cataclysm on the brink of a catastrophe. An immense blast of anomalous energy transforms the Zone: the once reliable and relatively safe roads are no longer so, the landscape is wiped clean by outbursts of anomalies, and previously unknown areas appear on the Zone map. Stalkers and expeditions perish or end up isolated within the lost territories.

LukeFerreira says

This review may contain spoilers

7/10 - Agree Disagree

Clear Sky is my least favorite one from the series, I consider it to be a good game in general but a bad Stalker game:

Pro:

-New areas that were very well done.
-The main character is an extremely interesting-looking individual... Even if you don't really know anything about him.
-Combat is the core of this game, expect to kill more people in CS than you ever will in other Stalker game.
-The maps were extremely well-done, even though CS is my least favorite game, it's maps are definitely my favorite ones, Limansk and the hospital just blew my mind.
-You get to witness some major events that you only heard about in ShoC.

So-So:

-Story doesn't feel as serious as in the other games, some people even go far enough to consider it fan-fic due to cheesy lines and the alteration of some character voices for the worst (Strelok being an example, he sounds like a teenager in CS).
-Even though this is a prequel, a few things that happen don't make much sense... Just roll with it and move on, try not to think about it too much.
-They had the right idea when adding the new artifact hunting system to this mod, artifact variety and respawn in anomalies feels stactic and uninteresting though.
-The ending offers you a very interesting cutscene... For Strelok. Scar simply vanishes, it feels like his only purpose to the game developers was to be "there" and then just disappear, almost like a scapegoat.
-Some parts of the zone look too much younger than it's sequel, nothing you shouldn't overlook it too much though if you consider the fact that they wanted maps to look more alive in CS.

Con:

-Failction Wars, they were supposed to be dynamic and rewarding, but end up being a chore more than anything else, plus the constant spawning and movement of NPC squads make the game feel more like a large online FPS map than The Zone, you will have very little imersion in the zone due to Faction Wars... At least they are completely skipable as far as the main story is concerned.