The Solitude of Prime Numbers by Paolo Giordano follows the lives of two friends from childhood into adulthood.  The central characters are both scarred by early tragedies, which brings them closer to each other than to other people, yet still, those tragedies remain a barrier.

The novel opens with Alice as a child, her dislike of skiing, and her father’s oppressive persistence that she ski.  Alice crashes and is forever disabled with a leg that drags.  Also, as Alice ages, she is crippled through anorexia.  The eating disorder does not cripple her physically for years to come, but it does cripple her emotionally as she hides the secret from those who love her.

Mattia is a twin, a gifted math prodigy, and a caretaker for his sister, Michela, who has a cognitive impairment, which is never explicitly named.  Mattia resents Michela and feels burdened by her.  When they are both invited to a birthday party (their first invitation ever), Mattia abandons Michela at a nearby park and tells her to wait.  She is gone when he returns and never found.  Did she drown?  Was she kidnapped?  Mattia and his family never know.  Mattia grows up with his guilt, which his mother adds to through blame, and begins to self-harm himself through cutting.

In high school, Alice and Mattia meet.  They don’t fall in love.  Or, perhaps, they don’t fall in love at once or together.  Also, it is never stated, but it seems that Mattia might suffer from a mild form of Asberger’s syndrome.  Due to Mattia’s social awkwardness, he is often confounded by Alice, or doesn’t know how to respond to her actions.

Instead of falling in love, it might be better to say they fall into understanding.  Both have scars plain to see on the outside of their bodies, but the deeper scars, the anorexia and guilt, are visible mainly to Alice and Mattia.  They know one another and accept the other person.  There are no demands or questions.  Instead, their relationship builds on acceptance and respect.  Will that acceptance and respect be beneficial or will that lead to their continued isolation?  The question is left to the reader and depends on the reader’s interpretation.

The Solitude of Prime Numbers is a portrait of two young people finding their place in the world.  It’s poignant, beautiful, and shares an interesting perspective of two people, twin primes, forever near one another, but divisible only by I.