This is a great collection of classic sci-fi stories that I highly recommend! I actually hadn't read any Stanislaw Lem before and am now keen to read more.

It is always fascinating to dive into visions of the future from the past, and many of the questions raised in these stories are timeless. The stories are arranged by publication date, and it is interesting to see their focus shift over time.
This would almost have been 5 stars overall, but a recurring theme in some of the stories really annoyed me, so I deducted 1.

Story by story:
1. The Hunt: This is really a story about humans and humanity. Very sad start to the collection, but I liked it.
2. Rat in the Labyrinth: The first of multiple stories dealing with aliens coming to earth, and the possible nature of alien life. This was a novel take on that for me.
3. Invasion from Aldebaran: One of the shortest in the collection, and also one of my favourites. Another first-contact story, but this time a humorous take. Love it.
4. The Friend: The first of several stories dealing with artificial intelligence, and my favourite of those.
5. The Invasion: As the name suggests, another story about aliens coming to earth, and maybe my favourite story in the whole collection. The major theme is again the nature of life, which is alaso touched upon in multiple later stories, including those about artificial intelligences, but I think this is the best.
6. Darkness and Mildew: A creepy and mysterious story that leaves much in the dark, that touches on multiple issues relevant both to its time of creation and today, but leads them more in an absurdist direction. I enjoyed this a lot, too!
7. The Hammer: Another artificial intelligence story that I rather enjoyed. Its central themes of trust in technology and what information to trust are still relevant today.
-- So up to here, I would have given the collection 5 stars. Not a single miss so far. --

8. Lymphater's Formula: I liked the format of this; as the reader we read one side of a conversation, it's like we are addressed by the narrator.
But this story is also the first manifestation of Lem's idea of what intelligence ultimately means, and that really annoys me (what I was referring to above)! One, I think Lem is wrong, and two, while his stories touch on so many interesting aspects of genuine science, it's also deeply unscientific. Lem's idea of intelligence, based on this story, as well as no. X and X further down, is that it amounts to basically telepathically reading the state of the whole universe and being able to calculate and know everything about it. But that's just magic. Of course what "higher intelligence" consists of is speculative, but the idea that it is just magically knowing everything that does happen or will happen without sensory/data input really rubs me a wrong way in stories about otherwise serious science.
Consequently: My least favourite story in the book, although it has multiple promising aspects.
9. The Journal: This is a story in a mysterious format that is difficult to read and almost incomprehensible, until you get to the explanation at the end; then you can go back and really understand it. Interesting; middle of the road in this collection for me.
10. The Truth: Another one about the nature of life and intelligence, but more believable and less woo-woo than Lymphater's Formula, so I enjoyed it a lot more. Here we're back in the realm of stories that make this book worth reading!
Also interesting to see it talk about the challenges of keeping plasma stable, which is still an engineering issue 60 years later (although it does not in fact cause explosions, it just means that the plasma cools down and we still can't commercially use nuclear fusion for power generation).
11. One Hundred and Thirty-Seven Seconds: Different to Lymphater's Formula, but annoyed me for the same reasons. This does have some interesting ideas about time as a dimension, but those cannot make up for the harebrained idea at its centre.
12. An Enigma: Short, sweet story to end the book. Another one that's more humorous, with serious undertones. Really nice to close out the collection so I can remember that Lem overall is brilliant.