Solaris is a 1961 philosophical, classic hard science fiction novel by Polish writer (and trained physician) Stanisław Lem .
The book centers upon the themes of the nature of human memory, human experience, and the different challenges (and the ultimate inadequacy) of attempting human communication between human and non-human alien species.
Contrary to popular belief (due to the focus of its multiple film adaptations) it is NOT a love/romance story.