I myself read and am inspired by Lem because of a few things, first that come to my mind are:
- the unmatched richness of ideas in his books,
- the climax of his 'serious' books (like tales of Pirx or Fiasco and Magellan's Nebula ) which can be counterbalanced only by...
-...the feel of his 'funny' books (like Mortal Engines).
And above all:
- his writing style, which means the language he uses, at least in Polish, I don't know how it looks after translation.