The Chain of Chance — Stanislaw Lem

An ex-astronaut investigates a string of potential murders in this novel by the Kafka Prize�"winning author of Solaris.

Vacation is supposed to be relaxing. But while traveling in Naples, several American tourists die in a most macabre and unusual way: committing suicide in a fit of madness. The cases are too similar to be coincidental, and the prevailing theory soon assumes that a serial poisoner is on the loose.
 
Called in to investigate, and stem the rash of death before it becomes an epidemic, is a former astronaut from the States. As he follows the path of the last victim, he is confronted with a mystery that proves the truth is always stranger than fiction -- and that we are all casualties of fortune in the end.
 
Called “a Jorge Luis Borges for the Space Age, who plays in earnest with every concept of philosophy and physics, from free will to probability theory,” Stanislaw Lem now tackles the suspense genre with his famed intensity and intelligence, weaving a taut and enigmatic tale as only a great novelist can (The New York Times Book Review).