Thomas Mallon wrote Henry & Clara, and I am one of the few on the forum that didn't care for it.
I wouldn't consider Epstein's book a "must read", but it's a good one to read, if you can get past it's shortcomings. It does have "source" notes.
(But I must confess, I'm a fan of Ruth Painter Randall, and I prefer her book)
So when is this "Old Enough To Know Better" supposed to kick in?