Seven Years by Peter Stamm
"Alexander is torn between two very different women. Sonia, his wife and business partner, is everything a man could want: intelligent, gorgeous, charming, and ambitious. But when the seven-year itch sets in, Alexander soon finds himself rekindling an affair with his college lover, Ivona. The young Polish woman who worked in a Catholic mission is the polar opposite of Sonia: dull, passive, taciturn, and plain. Despite having little in common with Ivona, Alexander is inexplicably drawn to her while despising himself for it. Lost between his highbrow marriage and his lowbrow affair, Alexander is stuck in a spiraling threesome."--From front jacket flap.