The Infinity Between Us by N.S. Perkins

Eighteen years of summers spent in a beach house in Ogunquit, Maine, have brought Violet Mitchell and Will Seaberg together. For two perfect, beach-filled months every year, they spent every waking minute together. First as friends, until one summer changed everything.
But before the two even had a chance to claim the love they’d spent their entire lives creating, disaster struck, tearing the two lovers—and their families—apart.
Heartbroken and haunted by the memories of that fateful summer, Violet struggles to move on from the past. Still, she promises herself to never contact Will again. But five years later, when Violet arrives to finalize the sale of the property, she finds Will right where she left him: sun-kissed, loving, and so incredibly sorry.
At first, she wants nothing to do with him, but Violet soon realizes that it’s inevitable and that the past she was running away from might actually hold the key to the love and the happiness she believed was stolen away from her five summers ago.