I'm not an authority as such, but I read the McCullough book the miniseries was based on, and I've read much of the correspondence between him and Jefferson and between him and Abigail, and I'd say, just from my layman point of view, the miniseries was fairly accurate, with one exception: John Adams, in his correspondence at least, was far more aware of his flaws and less desirable personality characteristics than was portrayed in the miniseries, but he was much more forthcoming about his flaws the older he became. He often said pride and vanity were his chief sins.