I absolutely love this book. It is not only a terrific story of a woman's interior life and personal development but it is a very realistic picture of a real "marriage" and how people rationalize and defend the choices they make. At the same time, the author gives hints to an impending sense of doom and suspense that comes together at the end in a surprising and very satisfying way.
It is beautifully and intelligently written and in a strange way offered me insights into things I have struggled with in my life.
I am intentionally not telling anything about the plot line because I knew very little about the book other than it was recommended by a source I trust (NYT BOOK reviews? NPR?) and Amazon's comparison mentioned Gone Girl. For me, this was far far better than Gone Girl, which I also enjoyed.