This book has been on my list for awhile. Solaris is about the alienness of aliens, and how ultimately two such diverse species are incapable of fully understanding each other. Humans, in their common hubris, discover a planet that is essentially a giant ocean of a brain and go to study it. Needless to say, the species with the larger brain ends up studying them. This brain can manipulate the humans and cause them to see what they feel the most guilty about, driving most of the visiting astronauts insane. Kris Kelvin visits Solaris and is in turn visited by his dead wife, Rheya, who died not long after they married. At first she behaves just like the deceased wife, but she gradually changes.
At times the translation from the Polish was a bit clunky (loads of filters and some awkward phrasing) and at times the book divulged into long ruminations of the astrophysics behind the alien, which I found rather dull. Aside from that, it was an engaging read that raised interesting philosophical points about human nature and the effect the brain can have on the body.