The Woman Inside by E.G. Scott

Rebecca and Paul have the perfect marriage or did before Paul's construction business went sideways, Rebecca's Pharmaceutical Reps career and her sampling went off kilter and Paul's eyes began to stray - you get the idea. So now after almost twenty years we have the perfect disaster for the perfect marriage. Each spouse is holding back key secrets, each is far from being the perfect partner and each may have a good reason to eliminate the other. Throw in a psychotic jilted lover and a murder or two and you have the perfect plot for an edge of your seat thriller. You won't know what the heck is going on right up until the unusual, but oddly fitting, ending and you can start to breathe again. Perfect for anyone who loves their thrillers full of unreliable witnesses.