One True Loves by Taylor Jenkins Reid

 In her 20s Emma Blair marries her high school sweetheart, Jesse. They build a life for themselves, far away from the expectations of their parents and the people of their hometown. They travel the world together, living life to the fullest.

On their first wedding anniversary, Jesse is on a helicopter over the Pacific when it goes missing. Just like that, Jesse is gone forever.

Emma quits her job and moves home in an effort to put her life back together. Years later, now in her 30s, Emma runs into an old friend, Sam, and finds herself falling in love again. When Emma and Sam get engaged, it feels like Emma's second chance at happiness. That is, until Jesse is found. He's alive, and he's been trying all these years to come home to her.