UnChristian is an empirical effort to examine how those "outside of the church" view Christianity. The research was done by David Kinnaman from The Barna Group, sort of a Christian Gallup Polling organization if you will.
The subtitle reads "what a new generation really thinks about Christianity...and why it matters". So as you might infer research was primarily focused on those aged 16-29. Which is a crossing of two generations: "the leading edge of the Mosaic generation and the trailing half of the Buster cohort". Throughout the book, Kinnaman provides well defined terms so even if you disagree with them at least you know up front with what you are not agreeing. Also, there is just the right amount of graphs/charts/pictures to know that this is great research, without feeling like a boring communications class presentation.
The overall "posture" of the book seems to be towards born-again evangelical Christians. Kinnaman seems to be peeling back the curtain for those folks that are along his own theological lines of thinking. He'll use the words "we" and you're not sure if that means Christians, or those that subscribe to particular doctrines within Christianity. Kinnaman does lay out different "tiers" to Christianity:
Self-identified Christians, Nonevangelical born again Christians, and Evangelical Christians. Since no one likes a mega-post, and Kinnaman has essentially written this book for an evangelical audience, here's his definition: (which is found in a small "glossary" in the back, great idea)
Evangelicals are "born-again" (meaning they have made a personal commitment to Jesus Christ, and believe they will go to heaven when they die as they have confessed their sins and accepted Jesus Christ as their savior).
Evangelicals also meet the following criteria-
1. saying their faith was very important in their life today
2. believe they have a personally responsibility to share their religious beliefs about Christ with non-Christians
3. believe that Satan exists
4. believe that eternal salvation is possible only through grace, not works
5. believe that Jesus Christ lived a sinless life on earth
6. asserting that the Bible is accurate in all that it teaches
7. describe God as the all-knowing, all-powerful, perfect deity who created the universe and still rules it today.
Kinnaman's definition of evangelical did not consider any denominational affiliation or requisite for church attendance.
This could be a misinterpretation on my part, but evangelicals are the audience to whom this book is written. This makes sense, because that is where David Kinnaman is coming from. To me, that is a fundamental (no pun intended!) factor in how one will receive the information. If you are not a part of the "we" that Kinnaman addresses, you could be in for a bumpy ride. If you're wondering whether I am on the fence on this, I happen to agree, if I had to pick yes or no, with Kinnaman. I would identify myself as an evangelical, with only a slight amount of trepidation given his definitions. But again, Kinnaman is very upfront with this, and kudos to him for not being wishy washy nor arrogant in his assertions. We could go round and round about the definition of "evangelical" and his criteria, etc. The most important part of the book is not what I've started out discussing, the most important part is the research and what it reveals about the state of the church in relation to the world around it.
So, now that you understand the basic premise of the book, and equally importantly the assumptions ( I'm not saying "bad" assumptions) behind the audience let's get to the good stuff.