A Perfect Vacuum is a peculiar text, even in the Sci-Fi genre, even when considering Lem's body of work. As you will know from the very beginning, it's a book of fictional scholarly reviews of various fictional works. It's also a mixed bag - some are extremely funny and creative, while others tend to drone on aimlessly. My favorites would have to be: The one about a story written strictly in a negative form ("this and that did not do this, this did not happen", etc.), the review of a book about the mechanics of artificial consciousness, and definitely the one about Robinson Crusoe. In all his works Lem's positively obsessed with our inability to connect to one another, and in Les Robinsonades this takes a very schizophrenic turn, quite similar to R.D. Laing's "The Divided Self".