Trick Of The Dark by Val McDermid

When disgraced clinical psychiatrist Dr. Charlie Flint receives an anonymous package of press cuttings detailing the brutal murder of a groom on his wedding day at Oxford, she is drawn back into the cloistered world of her alma mater. The bride, Magda, is the daughter of Charlie's former mentor, who suspects that the real killer is Jay Macallan Stewart—a wealthy dot-com entrepreneur, author of a bestselling 'misery memoir,' and Magda's charismatic new lesbian partner. While Charlie battles her own personal demons and a destructive infatuation with another woman that threatens her marriage, she begins to untangle Jay's past, uncovering a chilling pattern of convenient deaths that suggests she may be hunting a brilliant, ruthless serial killer.