Roadside Picnic tells a story about an alien visit to earth, however they all already left and only some of their stuff remained in incredibly dangerous Zones. At the beginning of the book we follow Red, a Stalker, they wander into the Zone and try to escape with their lives, if they are lucky they will bring some alien artifacts and sell them to the highest bidder.

The book is much more firm that the Zone was created by aliens, and brings you to question that, if there where aliens, would they try and talk to us or even see us as intelligent?

The story was heavily adapted for the games (called S.T.A.L.K.E.R.), but I also enjoy them very much.