This is a difficult book to review, because the author hides a key element of the plot until about a third of the way through the book. If a reviewer mentions this key plot element, the reviewer subverts the author's intention of drawing you into the story in a particular way, and with a specific perspective. But any discussion of the book that doesn't mention the hidden plot point leaves a reviewer....hanging. The review can't mention the issues that make the book so unique and compelling. It's also going to be difficult to draw in the readers who are most likely to be interested in the book.
Most reviews discussed the hidden plot point.
Personally, I thought it was a wonderful book, even though I knew the secret. My book group said that they couldn't imagine reading it without the surprise -- one member even said that the revelation transformed the book from not particularly interesting to one of the most compelling books that we've read.
You can make your own judgement: this book was short-listed for a Man Booker prize in its year of publication, and the internet is lousy with spoilers, if you're interested in tracking down that kind of review.
I'm going to avoid the issue entirely by addressing a relevant but unrelated question: is this book SF?
What makes a book science fiction? Or, 'SF' as I like to think of it, where 'SF' means 'speculative fiction'.
Now that's a question with many answers, and a question that deserves a much longer and more thoughtful analysis than I'm planning to stick in a book review.
One answer is very simple: SF is written by SF authors. Karen Joy Fowler....does she qualify? Maybe. She hangs around with SF authors, like Pat Murphy. Fowler is also one of the founders of the James Tiptree, Jr award, given each year to the SF work that best explores the meaning of gender. So at a minimum, Fowler has tight ties to the SF community.
Another answer: is the book filed in the SF section of your bookstore or library? Hm...second point in favour. I found my copy in the SF section of Munro's bookstore in Victoria.
Third answer: does it read like SF? Again, yes. As is typical with SF, the story explicitly starts in the middle. SF generally launches into the middle of a story, situation, or future that you'd never have imagined for yourself, and it's only as the book progresses that you begin to understand what's going on. Why is SF structured this way? Mostly because starting a novel with a bunch of exposition about the universe you're in, the future you've immersed in, or the technology that the story is discussing would be a very very boring way to start a book.
Fourth answer: is the book about character, is it about events, or is it about ideas? The *best* SF (IMHO), is about ideas, and We are all completely beside ourselves is definitely about ideas. Big ideas, fundamental ideas about our society. Check.
Final possible answer: is the book about science or technology? Contrary to popular opinion, IMHO, this is the weakest test. In fact, this is why I prefer to think of SF as 'speculative fiction' rather than 'science fiction'. Science fiction is, I guess, a fiction that explores science, science futures, or the implications of science on society. In its degenerate form -- as long as you understand that I'm using 'degenerate' in its most positive possible sense -- science fiction is fiction that includes specific scientific innovations like space travel and laser beams. And battles. And very very big bangs. While speculative fiction is simply fiction that asks 'What if'.
We are all completely beside ourselves definitely asks 'What if'. Check again.
So, if you enjoy SF, particularly thoughtful, well-written SF that has compelling characters and asks challenging questions, you'll enjoy We are all completely beside ourselves.
But you are also very likely to enjoy the book even if you would never voluntarily read a book with a space ship on the cover. There are no space ships in this book. It takes place in the present (okay, 2007, but that's when the book was published), not the future. And it does not involve a single piece of uninvented technology.
It only starts in the middle, and takes you to an unexpected place.