If you really want to get the most out this book, just jump in and read it. Don't ask your friends if they have read it, don't google it or read reviews. Perhaps even avoid the blurb on the back cover. In short, take every possible precaution against discovering the big plot twist which gives the book both its intellectual interest and its emotional punch.
Avoiding spoilers makes it difficult to say much about the book, beyond the fact that it is a family story with a difference. The narrator is wry and self-deprecating, while all the time delivering bang-on observations of human behaviour, relationships and life in general. It raises a whole host of philosophical and ethical dilemmas, without ever becoming dogmatic or preachy. Oh, and you might like to have some tissues ready for the ending.
The author, Karen Joy Fowler, also wrote The Jane Austen Book Club. We Are All Completely Beside Ourselves won the 2014 PEN/Faulkner Award for Fiction and was short-listed for the 2014 Man Booker Prize.