I, amusingly, had to interlibrary loan this because the Book Nobody Read is out of print. And then my copy had FIVE barcodes and spine labels from other stolen books stuck in it because I assume the thieves took the title seriously.
I really enjoyed it, but I’m a librarian. Not sure non-librarians and non-astronomers would have liked it so much, though. I particularly enjoyed the retrospective of how much more of a pain in the ass research in archives and special collections used to be.
Alfred Lansing’s 1959 book “Endurance: Shackleton’s Incredible Voyage,” about a 1914 Antarctic expedition, certainly reads like fiction, but it’s not. It’s a very compelling read.
I see now that it was mentioned a couple of times upthread – I swear I read it through!
I’m surprised no one’s mentioned any of the World Without End series by Ken Follett. Pillars of the Earth was a really engaging book, and I lked the idea of following the path of the families through time.
I highly recommend The Reckoning: The Murder of Christopher Marlowe by Charles Nicholl.
It’s a very carefully researched and gripping account of an Elizabethan murder mystery. How and why did the poet Christopher Marlowe die?
It opens up the dark and devious world of criminals, con-men and spies (often the same shady individuals were both criminals and government spies) in the London underworld. If you thought John le Carré novels could be complex and devious, they are nothing compared with the reality of Elizabethan spies - they could teach modern spies a thing or two.
And, yes, the evidence seems to indicate strongly that Marlowe was a government spy, and was mixed up in the thick of complex plots, counter-plots, and double crosses.
The evidence is presented carefully, and though Nicholl never goes beyond the facts, he brings the whole era vividly to life. It makes for page-turning reading.
First, thanks to everyone for the recommendations in this thread! Some of them sound mouth-watering to me and I’ve bought several of them. 
I’d recommend 1066:The Year of the Conquest by David Howarth. It’s not long, and is absolutely engrossing.
I also loved (though it’s a bit earlier than the time period you said you were interested in) Clara Bow: Runnin’ Wild by David Stenn. If you’re interested in early Hollywood, it’s riveting, and reads very much like a novel - Stenn saves his final punch for the end.
Richard Feynman’s memoirs (Surely you’re Joking, Mr. Feynman and What do you Care what Other People Think) don’t read at all like fiction, because they’re not nearly plausible enough. If they weren’t true, they’d be completely unbelievable.
You’re surprised that no one has mentioned a book(s) of fiction in a thread asking for non-fiction book recommendations? :dubious: