For McClellan, you might look into Ethan S. Rafuse's McClellan's War, which attempts to explain him as something other than a puffed-up bad tactician. Refuse ties McClellan's cautious , conservative style to his past allegiance to the Whig party, and does manage to dispel some of the worst myths about him ( when he once famously refused to see Lincoln, for example, he was probably suffering from the malaria he picked up in the Mexican War). I'm not sure Rafuse succeeds in exonerating him from all his mistakes, but it's nice to read something that tries to make sense of him, doesn't treat him as merely a blundering prelude to Meade or Grant.