Stanisław Lem is perhaps the most famous of Polish sf authors. He has written some great books and imagined concepts like nanotechnology (prominent in his "Invincible" book) or virtual reality. I remember "Futurological congress" as the first book raising the question 'what is reality. It is quite similar to Dick's Ubik in this regard. Nonetheless my favourite Lem's book is "Fiasco" ("Failure"), a story of a an attempted contact between two space faring civilisations. It raises Drake's equation's question of "why are we alone in the universe", and is a nice description of a failed contact - no happy end here. "Golem XIV" is another one of my favourite, raising the question of what happens when AI becames sentient and eventually, more sentient then human - here Lem raises the issue of technological singularity. The book is written in a form of combined Golem thoughts print-outs and comments of suprvising scientists. Then there is "Lord's voice" - which is quite similiar to Sagan's Contact. Oh, and lets not forget the entire book ("Fictional vaccum") composed of nothing else but reviews of fictonal books :) Last, but not least, there is a fairly large series of what I call 'stories'. Those are books and antholgies whose heroes are either robots or the cosmonaut Ijon Tichy, and all are a cross between a child's bedtime story, a parody of something, and...well, it is difficult to describe. See wiki's entry on The Cyberiad for some more info and a specific example. I am not a great fan of those series of his works, but I know many who would disagree. It is a shame in his late years Lem have stopped writing books and instead writes newspapers essays against technological progress and prophetising civilisation destruction. A consensus among sf fans in Poland helds it that old age has finally cought up with him (he is 84 now...) and made him a little, well, senile...sad, to see such a great writer tumble. On the bright side, many of his works have been translated into English (and Czech and many other languages), so you can just go Amazon, grab some of Lem's Golden Age books and see how good a writer he once was for yourself :)
Now, Janusz Zajdel. He is much less known outside Poland, a shame - the Zajdel Award, the biggest Polish sf Prize (think Nebula) was not named after him by an accident. Majority of his books - all of them, now that I come to think of this - were 'distopias'. Wiki sais it as well as I could: His novels created the core of Polish social fiction and dystopias. In them, he envisions totalitarian states and collapsed societies. His heroes are desperately trying to find sense in world around them, sometimes (like in Cylinder van Troffa) they are outsiders from a different time or place, trying to adapt to the new environment. However, the main idea that is visible to any reader is to force the readership to compare their gloomy, hopeless sitation to what may happen in space environment if we transfer totalitarian ideas and habits into space worlds. Red Space Republics or Space Labour Camps, or both. See his article there for info on his specific books like Paradisia. If I were to compare him to some known Western author, I think Dick would be the closest. Perhaps it is good to think that Zajdel = Dick - drugs + communist regime experience. Or in other words, Dick had visions of living in utopias and distopias, and Zajdel lived in one.
That ends the pre-1989 section of Polish sf. There are a few more names I could mention, but the are definetly not famous, and quite forgotten even today. Well, ok, I will add one more: Snerg-Wiśniewski. I have yet to read his classic, the "Robot". But one book of his I have read I will remeber forever: "Według Łotra" ("According to the Bandit"). It is a story of a Messiah in dystopia, told by one of the two bandits who would be crucified with him, eventually turning into an Ubik-like questioning of what is real and what is not. If one likes Dick and Zajdel, then Snerg is another must read.
Sapkowski, now, Sapkowski is definetly a post-1989 success story... Without a doubt, he greated a great fanstay series. "Wiedźmin" - 'witcher', 'hexer' (word invented by Sapkowski) is a story of a superhuman fighter, Geralt. Sounds boring? Well...a cynical and intelligent superhuman figher, who belongs to the cast of monster-killers. Once essential to the survival of the humans in this word, he and the few remaining members of his caste are feared and hated by everybody, treated like scum - well, scum that can kill. Add to it a great world - a New World, where humans nearly drove other races (elves, dwarfs) to the extinction, the world were realpolitik and money rule the day, and where the 'dark empire' of Nilfgaard is preparing to conquest the small kingdoms of the north, brining progress, order and technology no matter wheter the 'northern barbarians' want it or not. And, if case you are wondering, Geralt doesn't give a XXX about big politics and such. However, it apprers some powerful people want to make him their pawn...well, the story is written beautifuly, the characters are great, the background world is amazing... In addition, Sapkowski can make one laugh - especially in the early Wiedzmin side-stories/mini novels, which are not so dark as the series that follows it. And yes, the story has ended after 5 books - Sapkowski wisely (IMHO) decided that enough is enough and attempting to turn his idea into 20+ series would kill it, so he envisioned a good end and ended the story where he wanted it.There is a RPG based on this world, a movie and a tv series (both of which unfortunately were done by total idiots who thought they could write better stories then Sapkowski and cut him out of the loop, with predictable results resulting in what I think is the worst fantasy movie ever (seriously, even TROMA couldn't have done it 'better'), and a computer game in-making. All in all, this is a great fantasy, one of the best I have read. I would call it at least as good as GRRMartins or Glen Cooks works, and much better then your average run-of-the-mill fantasy. I think he was translated into Czech, wasn't he, Martin?
Next time, I will tell you more about few other great Polish writers...