Four stars and a box of tissues.
The setup is almost unbearably good — she sees him through a bus window in December, they connect, then he turns out to be her best friend's boyfriend. Silver then has to sustain that tension for an entire novel and largely does. The will-they-won't-they is properly agonising rather than artificially prolonged, and the friendship at the centre of the story is written with as much care as the romance. My one complaint: the pacing in the middle third sags slightly. But the payoff is genuinely lovely.