TigerHawk is polling readers: "select that one book that best makes the case for government in America according to conservative principles or positions." I've provided one suggestion in comments: "any college-level economics textbook." Yet, I'm not altogether happy with my answer. Here's why.
I've previously described how economics combined with Jimmy Carter helped shift my politics from left to right. And I fervently believe that liberals largely fail to grasp elementary economic principles. For example, simple stuff like the price mechanism (how supply responds to demand; and, conversely, what happens when a product or service is "free"), cost-benefit analysis, the fact that the voluntary exchange called "trade" (and most economics) isn't a zero-sum proposition. All this, and more, is covered in any "intro to micro economics" text--hence my recommendation.
Yet this omits the foreign policy dimension. In truth, another important milestone of my political transformation was reading Whittaker Chambers's "Witness." That book forever buried the notion of a benevolent Soviet Union. It was central to the conservatism of William F. Buckley, and his admiration for the work got me to read it (sometime in the early 1980s). But, with the Soviet Union long-gone, I doubt "Witness" packs the same punch today.
And both such approaches (economics or geo-politics) can be dry stuff for many. Which reminded me of books that tackled those subjects with humor. Such as P.J. O'Rourke's "Parliament of Whores," and (my favorite) "Give War a Chance." But perhaps the humorous tack only convinces the already-converted.
Assistant Village Idiot suggested C.S. Lewis's "Abolition of Man". I skimmed it about 25 years ago, yet don't remember it--though AVI's recommendation convinced me to order and download it while writing this post. Most of the other votes are ultra-dry (The Federalist Papers) or ultra-unlikely to persuade (Sarah Palin's Going Rogue). My favorite as of this writing is the second vote: The Declaration of Independence. Only problem--lefties claim to have read it, and say it mandates socialized medicine.
My answer to TigerHawk's poll was a fudge--it's not one book. Plus I doubt a college text would be sufficiently stimulating for many lefties. So, I encourage readers to surf over to TigerHawk with better suggestions. And to debate them in comments here.
Finished C.S. Lewis's "Abolition of Man." It's three short essays on the fallacies educators employ when eschewing objective moral values. Lewis correctly says they purport to be teaching non-judgmentally, but actually are substituting modern mores and thereby obscuring language and learning for students. In effect, it's a short critique of post-modernism.
I think it would be ineffective as "the" book. Partly because it's a product of its period (published in 1943), and of the unfortunate mid-20th Century detour of Philosophy into solely Philosophy of Language, a digression thankfully passed. I don't disagree with Lewis's premise that long-held morals and ethics are the touchstone for society. And I loved his slicing and dicing those who use tautology to avoid acknowledging that they merely would substitute new values for old--all in the name of dissecting, or moving beyond, values. Yet I wasn't enthralled, partly because of his presumption of "natural law," which is fine in Philosophy but can lead astray when applied to jurisprudence. I can't decide if he fell into the error of assuming that science and faith are incompatible.
For all its virtues, I found "The Abolition of Man" too narrowly focused on ethics in education to answer TigerHawk's call for the best single work about conservative principles.