An interesting set of responses, kind of what I was hoping for. I'm bemused that a couple of people seem to regard Lem's work as equivalent to YA fiction, which strikes me as putting Orwell's Animal Farm in the same category, or regarding Vonnegut's Sirens of Titan as an SF adventure of the same level as L. Ron Hubbard's space operas.
Despite that, I like sunandshadow's comment about "fun and childlike satire but not really happy". I agree with that. Lem is not an optimist, but it's worth remembering that he, like Vonnegut, has bad personal remembrance of WWII, being a young adult in Poland at the time, before the Russian Communist domination. In that context it's also worth noting that Poland was the first "Iron Curtain" nation to throw off that domination, by free election, in 1989. And I remain mystified by JAR's comment about Lem's politics, which I still fail to find major expression of in his fiction.
Eastern Europeans have produced a number of satirical fiction writers who adopt the technique of childlike fable (much as Orwell did in Animal Farm) for serious social commentary. Among these are Carel Capek (who invented the word "robot") and Slawomir Mrozek from Czechoslovakia, and, of course, the great Franz Kafka. In his best work, Lem settles nicely among them.
For those who haven't read Lem, I'll post a characteristic passage that illustrates his dry and deadpan wit, which I greatly admire:
"There are papers and programs that give all the news and those that give only the good news. Until now they had been feeding me the second kind, which is why at the base I had the impression that the world had truly improved after the signing of the Geneva Agreement. You would have thought at least the pacifists were happy, but no. A book Dr. Lopez loaned me tells the story of our new society. The author shows that Jesus was a subersive sent to undermine Jewish unity with that love thy neighbor business, on the principle of divide and conquer, which worked, and which a little later brought down the Roman Empire. Jesus himself had no idea he was a subversive, and the apostles too were in the dark, having only the best intentions although everyone what is paved with good intentions. The author, whose name I have unfortunately forgotten, says that anyone who proclaims brotherly love and peace on earth should be immediately arrested and interrogated to see what his agenda really is. So it's not surprising that the pacifists have changed their tactics. Some have taken up the cause of delicious animals. There has nevertheless been no decline in the consumption of pork chops."
-- from Peace on Earth
YA? Something tells me no, but then, you might be surprised how astute your 13-yeaar-old can be about such things.
caw