Be Mine by Laura Kasischke
On Valentine's Day, Sherry, a college professor finds an anonymous love note in her locker: Be Mine. Her life has been a little askew since her only son left home, and though she has a happy, solid marriage with her husband, Jon, with whom she lives in her beautiful, isolated house in the country, how exciting is sex after twenty years with the same man? So she's intrigued, and not a little flattered by the notes as they continue, and embarks on a passionate and erotic affair. Her son's school friend, Garrett, is witness to the affair, her best friend, Sue, normally garrulous and chirpy, is strangely silent, and unusually, Jon is aware of the situation, adding some excitement to their own relationship. Then Garrett goes missing, swiftly followed by Sherry's lover, and what has seemed a very easy game to play, suddenly spirals out of control.
Be Mine is a stunning, compelling erotic thriller of how dangerous things can become when the boundaries of acceptable behaviour with family and friends are pushed to the edge.