In case the cover doesn't spell it out for you, Mary Roach's writing tends to the irreverent. I'd read one of her previous books (Stiff: The Curious Life of Human Cadavers) and so I had a pretty good idea of what to expect with this one: lots of biology, quirky research and some gross-out factors. I picked up this one to read on vacation a couple of months ago, and while it is not the kind of book that I can read straight through--I need a true narrative for that--I loved reading this one a few chapters at a time and feeling both enlightened and entertained simultaneously.
Roach (and one feels that growing up with this surname certainly was instrumental in developing the author's sense of humor) introduces the reader chapter by chapter to the entire digestive tract of the human body, soup to nuts, as it were, beginning with the relationship between scent and flavor/taste and ending with the excreta, with diverting stops in between for saliva, the art of chewing, and stomach acid, among other things. Her style is to jump right in and get involved with her research, whether that means sampling the muktuk (uncooked narwhal skin) offered by her Inuit hosts ("exquisite") or bearing the moderate discomfort involved in viewing her own appendix or ileocecal valve through modern surgical techniques.
Here's one sample of her trademark humor that doesn't involve any ick-factors: "Animals' taste systems are specialized for the niche they occupy in the environment...This includes the animal known as us. As hunters and foragers of the dry savannah, our earliest forebears evolved a taste for important but scarce nutrients: salt and high-energy fats and sugars. On the African veldt, unlike at the American food court, fats, sugar, and salt were not easy to come by. That, in a nutshell, explains the widespread popularity of junk food. And wide spreads in general."
This book is many things, but foremost it is fascinating, and that more than makes up for the occasionally off-putting sections that I don't recommend reading within an hour of eating. Roach concludes, almost poetically, "Most of us pass our whole lives never once laying eyes on our organs, the most precious and amazing things we own. Until something goes wrong, we barely give them a thought. This seems strange to me. How is that we find Christina Aguilera more interesting than the inside of our own bodies? It is, of course, possible that I seem strange. You may be thinking, Wow, that Mary Roach has her head up her ass. To which I say: Only briefly, and with the utmost respect."
NB: I read an advance readers copy of this book provide to me at my request from my sales rep. This book is published by W. W. Norton.