This is due to poor translation - Lem is generally regarded as a master of style. Polish sentences tend to be longer, not unlike German, because highly inflective grammar allows for it. It is not the case for languages with simpler grammar like English, of course.
>>alkyon+(OP)
Partially, yes. But I'm a native Polish speaker who reads a lot, and still consider Lem a challenging writer. He did like long and complex sentences with diverse vocabulary.