Oh William! : a novel
(Book)

Series information from goodreads.com.

Lucy Barton is a writer, but her ex-husband, William, remains a hard man to read. William, she confesses, has always been a mystery to me. Another mystery is why the two have remained connected after all these years. They just are. So Lucy is both surprised and not surprised when William asks her to join him on a trip to investigate a recently uncovered family secret--one of those secrets that rearrange everything we think we know about the people closest to us.