Pirx the Pilot is one of my favorite Lem books. It contains four stories featuring young Pirx. All the stories are stand alone, and can be read independent of the others. The second story "Conditioned Reflex" is similar to 'Solaris', and drag at one or two points with a heavy descriptive language that was difficult for me to work through. The others three stories are quite good, and I would highly recommend this book.