Poorly executed, amateurish, obvious and full of simplistic errors.
I hadn't read any books specifically about McClellan before, so I was looking forward to this one, but it really failed to live up to expectations.
First, it seems like the author shoved in some information about Lincoln as an afterthought... knowing that he would sell more books if he included more Lincoln in it. The sections on Lincoln are very superficial. It's clear that Waugh cares more about McClellan and has more source material on him.
Second, this is one of those books that has a simple, obvious thesis, that either didn't need to be written at all (because others have already covered the material) or it should have been written in a much shorter format. Waugh and his editors chose to write this book in such a way that a 218 page book as 25 chapters and an epilogue. So the average chapter is only about 8 pages long. Then, further cutting down the page count, most chapters end on a right page, the following left page is left blank, and then almost 1/2 of the page that starts the next chapter is filled with the title and no content. If you cut out all of the blank space, this book would easily be 40 pages shorter.
Third, there are some very simplistic historical errors that the author should have not made, and the editor should have caught. A few notable examples... he writes that the second battle of Manassas began at the Brawner Farm (which is true), but he says that the farm is 7 miles south of Manassas (which it is not... it's north of the town). He refers to George Gordon Meade as "Gordon Meade". He states that Johnson surrendered 9 days after Lee (it was 15 days later). He also says that Lincoln was "the last of 620,000 casualties of the war." That is wrong/insulting in several ways. First, the war wasn't over yet. As he pointed out in the previous paragraph, Johnson, let alone several other large Confederate armies, had not surrendered yet. Second, just because a person didn't die during the war (whenever that was) doesn't mean that they aren't casualties of the war. If a soldier was in the hospital with a wound, and didn't die until after Lee surrendered, that soldier is still a casualty of the war. You could even make the argument that any man who had his health reduced by the war, physically or mentally, was a casualty of the war. Finally, the 620,000 figure is commonly accepted, but outdated and unrealistic. It's more likely that closer to 700,000 men, or more, died as a result of the war.
So, overall, this is a book full of issues. I did learn a bit about McClellan and it is clear that the author made an attempt to use decent primary sources (although he did lean on a few a bit too much). For those reasons, I couldn't justify giving the book one star.