We'll Always Have Summer by Jenny Han (Summer #3)

Can Belly make a final choice between Jeremiah and Conrad? Find out in the conclusion of the New York Times bestselling The Summer I Turned Pretty trilogy from the author of To All the Boys I’ve Loved Before (now a major motion picture!).
It's been two years since Conrad told Belly to go with Jeremiah. She and Jeremiah have been inseparable ever since, even attending the same college—only, their relationship hasn't exactly been the happily ever after Belly had hoped it would be. And when Jeremiah makes the worst mistake a boy can make, Belly is forced to question what she thought was true love. Does she really have a future with Jeremiah? Has she ever gotten over Conrad? It's time for Belly to decide, once and for all, who has her heart forever.