Some on the Right, including several of Reagan's family members and former staff, go so far as to call this book "garbage" and a "political smear." Bill O'Reilly claims that it is a "laudatory book" and "100% accurate."
I think the truth lies somewhere in the middle.
I can't blame O'Reilly for wanting to share as many surprising facts about the former president as possible. And, considering the high esteem in which Reagan is generally held, it makes sense that people are less aware of his shortcomings than they are his successes. KILLING REAGAN is a nice reminder that even the greatest men in history were all-too-human and fallible, and I definitely have a better understanding of who Reagan was after reading this book. However, for those who have little knowledge of Reagan, KILLING REAGAN is not the place to start. Not because it contains errors (THE WASHINGTON POST seems to have uncovered 7 mistakes, 2 of which are relatively minor), but because the focus of the book is skewed in favor of the more "juicy" bits of Reagan's life. More time is spent discussing Nancy Reagan's reliance on astrologers than explaining how Ronald Reagan revived the American economy. Sure, the book credits him with doing so, but readers are given nothing in the way of specifics. Not that O'Reilly intentionally tried to do Reagan a disservice, mind. As far as I can tell, he simply considered "Reaganomics" to be common knowledge (read: boring) and was in a hurry to get back to the quirkier stuff.
But the real bone of contention about this book is the supposition that Reagan's Alzheimer's first became apparent during his presidency, despite not being officially diagnosed until six years after he left office. O'Reilly states that Reagan, during his presidential reign, had "good days and bad days"--language usually reserved for talking about someone who ought to be in a nursing home. O'Reilly feels that Reagan's success as president is all the more impressive in light of the inner battle he was being forced to wage, whereas O'Reilly's critics consider it the highest insult to claim that Reagan was operating on anything less than his full mental faculties.
The evidence O'Reilly uses to support his argument is weak in the extreme, and it is here that the book loses credibility. It certainly doesn't help that O'Reilly never bothers to source anything, forcing readers to either accept or reject his information out of hand. All of O'Reilly's other KILLING books so far have dealt with actual--rather than attempted--assassinations, and I'd be willing to bet that O'Reilly just couldn't resist the notion that Hinckley's bullet contributed to Reagan's death, either by triggering or perhaps accelerating his mental deterioration. The way O'Reilly looks at it, Hinckley really DID kill Reagan--though it took a very long time for it to finally happen. It's an attractive thought in light of maintaining the theme of these KILLING books...but the evidence just isn't there, despite O'Reilly's arguments to the contrary.
KILLING REAGAN suffers from taking too narrow a perspective on things. O'Reilly didn't want to interview the people still living who were close to Reagan, because he worried their opinions would be biased in Reagan's favor. So instead, he only interviewed people whose opinions about Reagan could be considered middle-of-the-road. At first glance, this might seem like a good idea, but there are definitely serious drawbacks to this approach. Imagine doing a book on Hitler and only interviewing people who thought he was "like, whatever."
But if anyone gets the shaft in this book, it's Nancy Reagan, who O'Reilly portrays as a modern Lady Macbeth. The way O'Reilly tells it, you'd think no one ever thought kindly of her--at least not until they saw the way she cared for her husband while on his deathbed. Couldn't O'Reilly have dug up at least ONE person with something nice to say about Nancy?
On a final note, I've always considered the KILLING series to be "creative non-fiction," rather than pure history. Since I've always regarded them as such, I don't feel scandalized the way other people do when it comes out they contain errors. That being said, I consider KILLING REAGAN to be the most problematic of the KILLING series and have given it a lower rating accordingly. Still, it's worth reading to get a broader understanding of Reagan, as well as some insight into the mindset of his would-be assassin.