The stories of a small Cape Cod postmistress and an American radio reporter stationed in London collide on the eve of the United States's entrance into World War II, a meeting that is shaped by a broken promise to deliver a letter.

"A novel about past mistakes and betrayals that ripple throughout generations, The Guest Book examines not just a privileged American family, but a privileged America. It is a literary triumph. The Guest Book follows three generations of a powerful American family, a family that "used to run the world." And when the novel begins in 1935, they still do. Kitty and Ogden Milton appear to have everything--perfect children, good looks, a love everyone...