Happened to read this book yesterday, and it's a mixed bag.
Firstly we have several more chapters on why McClellan and friends were so bad. These are essentially a continuation of his previous arguments.
However, we then have two very good chapters. "The revolt of the generals" covers the dysfunction that effected the Army of the Potomac's command structure after McClellan was removed, culminating in Burnside trying to dismiss almost the whole of the top level command before being relieved of duty. It of course has the typical swipes at McClellan one would expect from Sears; "McClellan had managed (at least to the satisfaction of the officer corps) to disguise the reverses of the Seven Days and shift responsibility and lay the blame on shoulders other than his own.". As if the entire officer corps of the Army of the Potomac were a bunch of shills to be conned.... This chapter should be read with the next; "In defence of Fighting Joe", a well written attempt to vindicate Hooker. Only putting these two together can we understand the authors overall intent, to build a picture in which Hooker's failure is the fault of others. Even the blurb on the back spells out that Hooker's firing was not justified in Sears' eyes.
Much of the rest of the book is taken up with examining other Generals and a pattern emerges, the Republican Generals are lauded and defended whilst the Democrat Generals are derided and subject to character assassination. In this I've come to the conclusion that Sears has a "Radical Republican" agenda, which makes his works much easier to understand.