The Sweetheart Deal by Polly Dugan. The book is being released by Little, Brown and Company on May 19, 2015.
Amazon says this about the book: The poignant story of what happens when a woman who thinks she's lost everything has the chance to love again.
Leo has long joked that, in the event of his death, he wants his best friend Garrett, a lifelong bachelor, to marry his wife, Audrey. One drunken night, he goes so far as to make Garrett promise to do so. Then, twelve years later, Leo, a veteran firefighter, dies in a skiing accident.
As Audrey navigates her new role as widow and single parent, Garrett quits his job in Boston and buys a one-way ticket out west. Before long, Audrey's feelings for Garrett become more than platonic, and Garrett finds himself falling for Audrey, her boys, and their life together in Portland. When Audrey finds out about the drunken pact from years ago, though, the harmless promise that brought Garrett into her world becomes the obstacle to his remaining in it.