Haven't read Roadside Picnic, but I've seen Tarkovsky's Stalker several times. How do they compare? Stalker on it's own is an amazing piece of art. The Stalker in the monologue at the end laments that no one believes anymore (this seems to be Tarkovksy's critique of materialism and probably got him in trouble with the Soviet censors) - it can also be seen as depressing, but there's that bit at the very end when Stalker's daughter does that telekinesis thing which can be seen as being a bit hopeful for the future.