I read where, yes, another author had sketched the bare outline for a book, but had pretty much abandoned it. Ambrose asked if he could take it over and run with it, even offered to give the guy co-author credits. The guy didn't think it was going to go anywhere, so he declined and told Ambrose to have fun and don't worry about the credits. So Ambrose did. And, of course, being an Ambrose book, it sold extremely well. So the guy was ticked and accused him of plagiarizing. Based on what I've seen/read so far, I'm gonna have to come down on Ambrose's side. The guy is too good an author/interviewer/historian to need to stoop to something like that.