The book tells the two intertwined stories of how the main character(who is a stand in for the author) meets and falls in love with his wife, and how he prepares to say good-bye to her as she dies of cancer. Using flashbacks the book moves from the present day, where plans are being made to say good-bye, to 30 years ago when the protagonists first falls in love. The chapters alternate between the present and the past with a couple of detours thrown in that explain revelations the main character has about his wife and his marriage.
The only criticism comes because the book is autobiographical the setting is among the literary set of upper middle class Manhattan. The couple in this book have access to more resources and advantages then an average person and they press those advantages to get the best care. Since this is autobiographical, this is only a small complaint but I do wish the more novelists writing about the struggles of a similar couple without the advantages being well off brings.
That said, the story is a good; especially the last half. As the twin narratives move toward a consummation, the tension in both narrative arcs draws the reader into the story. Most importantly the author tells a story and tells it well. There is enough tension and emotion in the subject matter of love, life, and death that a straight forward approach is all that is needed. All the writer needs to do is tell the story and tell how he felt. He does and the book is better for it.
A Happy Marriage is really a good piece of writing. It tells a story in a straightforward, honest manner and it does so with showing off how much work was behind the production of the story.