The Quickie by James Patterson

Lauren Stillwell, an NYPD cop finds her husband leaving a hotel with another woman, she decides that she has to beat him at his own game.  However her plan of revenge goes wrong and more wrong by the minute.  Lauren also must take a case that threatens everthing she stands for.  He is holding a secret that can blow her world apart and she is scared stiff.  With her whole world on the line she fights with everything she has and wins.