His works explore philosophical themes; speculation on technology, the nature of intelligence, the impossibility of mutual communication and understanding, despair about human limitations and humankind's place in the universe. They are sometimes presented as fiction, but others are in the form of essays or philosophical books. Translations of his works are difficult and multiple translated versions of his works exist.
Lem became truly productive after 1956, when the de-Stalinization period led to the "Polish October", when Poland experienced an increase in freedom of speech. Between 1956 and 1968, Lem authored 17 books. His works were widely translated abroad (although mostly in the Eastern Bloc countries). In 1957 he published his first non-fiction, philosophical book, Dialogi (Dialogues), one of his two most famous philosophical texts along with Summa Technologiae (1964). The Summa is notable for being a unique analysis of prospective social, cybernetic, and biological advances. In this work, Lem discusses philosophical implications of technologies that were completely in the realm of science fiction then, but are gaining importance today—like, for instance, virtual reality and nanotechnology. Over the next few decades, he published many books, both science fiction and philosophical/futurological, although from the 1980s onwards he tended to concentrate on philosophical texts and essays.
He gained international fame for The Cyberiad, a series of humorous short stories from a mechanical universe ruled by robots, first published in English in 1974. His best-known novels