Safe Haven by Nicholas Sparks

Quickie Spoiler: Kevin finds Katie but accidentally shoots himself dead. Jo is the ghost of Alex’s wife.

The Setup
Twenty-seven-year-old Katie Feldman is the newest resident of Southport, North Carolina, where she’s moved to escape a dark past. Soon, she becomes involved with thirty-something general store owner Alex Wheatley, a widowed father of two. She also befriends her neighbor, Jo, who encourages the romance.

The Twist
Katie finally tells Jo her secret: that she’s on the run from an abusive marriage. Jo pushes Katie to tell Alex, and when she finally does, he is supportive, and declares his love for her. The two become serious, unaware that Kevin, the husband Katie left behind in Boston, is hot on her trail.

The Spoiler
Kevin arrives in North Carolina, going on a violent rampage in order to bring Katie home. Though he does much damage, Kevin ends up dead by his own gun. In the aftermath, Alex gives Katie a letter that his terminally ill wife, Carly, had written before she died – a letter she didn’t want him to read – but to give to the next woman with whom he fell in love. After arriving home to find Jo’s house deserted, Katie thinks that her neighbor was a figment of her imagination, until she reads the letter – which tells her how to love Alex – and realizes that Jo (Carly Jo) was the ghost of Alex’s wife.