Other threads have listed a variety of paleo references for newbies, but it's tough to pass on a whole list of references to non-paleo folks when introducing them to the concept.
So, if you could only recommend one book (eBook or print) to serve as a "proper" introduction to the paleo/primal lifestyle, what would it be, and why?
It really depends on the learning style and history of the targeted reader.
They are just looking a solid approach in an entertaining (tough-loveish) format? Robb Wolf's The Paleo Solution: The Original Human Diet
They have a science-minded bent, but just want the overview? Gary Taubes' Why We Get Fat: And What to Do About It
They have a science-minded bent, but want all the details? Gary Taubes' Good Calories, Bad Calories: Fats, Carbs, and the Controversial Science of Diet and Health
They need the friendly, easy access version. Mark Sisson's The Primal Blueprint: Reprogram your genes for effortless weight loss, vibrant health, and boundless energy
Personally, I started with Sisson's work and website, and then dove into GCBC and loved it... but I'm a huge science geek.
I would give Sisson to my ( not steeped in science ) relatives, and I would would set the rest up with Taubes' Why We Get Fat.
Make sure to tell them that this is the first stepping stone, and the start of a great journey.
Chris Kresser (thehealthyskeptic.org) has what sounds to me like a good answer:
"One complaint I’ve had for a long time is that there hasn’t been a single book I can recommend without reservation to friends and family that reflects my views on nutrition. There are certainly some great books out there, but there’s almost always something relatively significant I disagree with that keeps me from giving my full stamp of approval.
I had come to the conclusion that I’d have to write this book myself, but I simply don’t have the time and don’t anticipate that changing in the near future.
That’s why I was thrilled (and relieved) to discover the Perfect Health Diet by Paul Jaminet, Ph.D and Shou-Ching Shih, Ph.D."
Primal Blueprint is simple and user-friendly.
Why We Get Fat is a great explanation of the science.
My personal favorite is The Paleo Solution, by Robb Wolf. It's entertaining and scientific enough for the skeptics. His podcast is also great and very accessible (and entertaining).
The problem is that if you show them just ONE book, they'll think its the "law" and not look at other resources. For example, I showed my parents Marks Daily Apple and Robb Wolf and now they're like "but you can't eat butter, why are you eating butter?! I can't go without butter!!" And I've had to show them other resources and that's just left them confused.
Show them PaNu, I think that's the easiest one to understand coming from SAD.
Or you can just dumb it down to this:
Eat Real Food, Don't eat Sugar or Grains, Don't eat more than 100 - 150 carbs a day. Eat lots of fat.