I think the last adult nonfiction tome I read was What to Expect When You’re Expecting.* This biography of Robert E. Lee is stunning. You should read it.**
*That was slightly after the Lower Canada Rebellion. Look it up.
**Caveat: I knew the author, Jonathan Horn, when he was a wee lad, but I only promote excellent books, really, honestly. I know lots and lots of writers (ok, some are dead, but I did know them), and I only hype the best stuff.