For all the shrill complaints, you'll notice no one points out any errors in this book. Indeed, most of the factual history in the book is solid and not even seriously debated by historians. For example - numerous memorials notwithstanding - all serious historians agree that the Confederates, not the Union, burned Richmond and many other Southern cities as they abandoned them. I learned a lot from this book, and I haven't found any serious problems with his facts for for the items I've looked into - although I don't think *everyone* would agree that President Buchanan was gay.
Like his earlier book, one of his central points is that accurate and complete history - with all its controversy and complexity - is simply more interesting than the sanitized (and sometimes just plain wrong) version we get in school or from historical monuments. I strongly agree, but some people are very uncomfortable with this view, as is clear from the other comments. He doesn't say our Founding Fathers were "despicable", merely that they were human beings with human flaws - some of them large. For example, he has a lot of good things to say about Thomas Jefferson, but it's a pretty serious omission to sweep the fact that he owned slaves under the rug. If you want to hear only good things about our major historical figures, do yourself a favor and *do not read this book*.
He does have a serious axe to grind with the South, but remember he's competing with books like "Slavery: as it was", which is still trying to paint an idyllic picture of black simpletons who really preferred being slaves (read some of the glowing reviews *that* book gets). We would probably complain if Germany still had monuments to Nazis, yet the South has many monuments vicious and outspoken racists.
That said, the book does have a few flaws. First of all, he really beats some things to death. For example, he objects to the use of the term "discover" for anyplace where Indians were already living. Fair enough, but he devotes quite a bit of the book to going through these on a case by case basis, and it just gets repetitive. I would have been happy for him to have simply made his case and then given a short list of examples.
Second, like his first book, he does interject a bit too much of his personal politics. Usually, this is in the form of explaining how certain monuments came to be, but sometimes it's about monuments that aren't necessarily inaccurate, but just "incomplete" in his view. While I don't think his views are necessarily wrong, these observations give the book a biased tone that it doesn't need to have. The book would still have plenty to say if it stuck strictly to facts and avoided analysis.
So, definitely read the book. Check the facts yourself if you don't believe them, and take the politics with a grain of salt.