The Solitude of Prime Numbers by Paolo Giordano
Your heart will ache for the characters, but you'll be compelled to read chapter after chapter.
Booklist review from Amazon.com:
Giordano’s deeply touching debut novel immediately thrusts the reader into the lives of two individuals, at the moment when each of their young lives takes a sharp turn toward painful solitude: Alice has been crippled in a childhood skiing accident, Mattia is consumed by guilt after playing an unintended but key role in his twin sister’s disappearance. Upon meeting in their early teens, they develop a frequently uncomfortable yet enveloping friendship. What follows is a beautiful and affecting account of the ways in which seemingly inconsequential decisions reverberate so intensely as to change a life forever. Translated from the Italian, this is a book about communication: in lacking a facility for self-expression, our stunted protagonists exist almost solely, and safely, in their own minds. Despite its heavy subject matter, it reads easily, due in part to the almost seamless translation. A quietly explosive ending completes the novel in just the fashion it was started, as an intimate psychological portrait of two “prime numbers”—together alone and alone together. --Annie Bostrom