It's hard to pin down a "typical" book of Lem's, but there are certain themes he returned to time and again. 1) The role of probability in life: "Chain of Chan

It's hard to pin down a "typical" book of Lem's, but there are certain themes he returned to time and again. 1) The role of probability in life: "Chain of Chance" and "The Investigation" (the former is much the better book) 2) The role of scale in our understanding of the universe: "His Master's Voice", "Fiasco" and "Solaris" all touch on this, and are all excellent (I have a special fondness for HMV as a book that describes how scientists actually think and work in a way that nothing else I've encountered does) 3) The role of systems of control in the future of humanity: "Memoirs..." and most of the Ijon Tichy stories fall into this category, and are in my view his weakest work, although "Return from the Stars" is a brilliant book on this theme. 4) The role of cybernetics in the future of evolution: "The Cyberiad" etc. The problem of the "silent universe" (explored mostly deeply in "Fiasco") is also one that comes up repeatedly, including a long and interesting essay in "Imaginary Magnitude".