Honestly, the postmortems I'm most interested in after this year aren't from Trump or even Trump's campaign. I'm much more interested in the GOP quislings who clearly knew that Trump was both unelectable and catastrophic and decided through whatever calculus that they had to support him anyway.
Paul Ryan would obviously figure heavily in this, but chief among them now has to be Mike Pence. It's not just that Pence spent months criticizing Trump for his behavior. Pence also spent his time as a politician advancing and supporting -- and putting into practical action -- policies like free trade and American interventionism that Trump has explicitly derided. Now he's disavowing everything in a day to be the running mate for a candidate that almost certainly can't win, that had to be forced to pick him, and who has made it as obvious as possible (I can't even say without coming out and saying it because he did come out and say it) that he does not like Mike Pence or want him to be vice-president.
How did Pence end up in this situation? What are his actual values, if anything? Who persuaded him to take this role, and how? What does he imagine he will get for it? Or did he have so few fundamental principles that he actively wanted to be Trump's running mate?
This is a book I would definitely read. If Trump somehow wins, it's a book history students will read when trying to understand how things came to this pass.