The first half of Hons and Rebels will be familiar to you if you've read Nancy Mitford's books, with vague Muv and roaring Farve, debutante balls, cold houses and all that.
But the second half is something else: it's 1930s Europe (including Britain) and the US, observed by someone witty, engaged and entertaining, who has the enormous advantage of being born into the incestuous British ruling class, but who can't accept the status quo.
This combination of personality and accident of birth -- along with the witty, honest writing style -- is what makes the book so special. It enables her to save hundreds of pounds (this in the 1930's) without ever getting a job, and then get Winston Churchill's charismatic, anti-fascist nephew, who happens to be her cousin, to take her with him to Spain. British reporters travel to the Basque Country just to report on the scandal of the runaway Peer's daughter, even as the Germans bomb Guernica. Later, she and her cousin Esmond get away with behaviour that would probably land a less well-connected person in the dock for theft.
I unintentionally tripled my knowledge of the political climate just before WWII in a few pages. Ms Mitford doesn't write as an expert or a historian, but as someone who was unusually well-connected, observant and engaged. Her point of view is unique in my experience. If she had been a man she would have been more active, and quite likely have been killed. If she had been a woman more like her mother or most of sisters, she would have devoted herself principally to incubating more aristocrats, perhaps with some memoirs or a novel or two to keep herself occupied.
I thoroughly recommend this book.