The “two peas in a pod” image conveys a cozy togetherness that belies the (absolute) solitude implied in the title. In one fell blow, the designer has conveyed the premise of the book: that the plot revolves around two characters drawn together by their shared loneliness.
A prime number is a lonely thing. It can be divided only by itself or by one: it never truly fits with another. Alic and Mattia are both “primes”—misfits who seem destined to be alone…When the two meet as teenagers, they recognize in each other a kindred, damaged spirit.