3.5*
The content is 5 stars. This was an absolutely fascinating story, and I would love to go back in time and have dinner with Virginia Hall and just pump her for stories because damn. She would have some good stories.
However, the reason I took off stars was the writing. While I finished the book in just a few days (this is a great subway read!) and it's very engaging while you're reading, it feels very surface level. I would have appreciated more time developing side characters besides two or three who get particular attention. Towards the end, a lot of names were thrown around that the reader has already seen, and I had to really, really search my memory to remember how they had helped or hindered Virginia. I also would have appreciated more tactics, how did all of Virginia's mission fit into the larger scheme of the war. A lot of the time, the writing felt like it was skimming her story because it moved so quickly. A month would pass, and we would be told that Virginia had done a lot of work, but there was no real discussion of what that work was.
But I really, really wish the author and editor would have chosen to integrate sources differently into the narrative. They're used as footnotes, and there's no reference in the text as to how the author acquired the information. For details such as numbers and troop movements, it doesn't matter as much, I don't think, because I assumed she took it from a report or other piece of information (though it would have been nice if the author integrated those in as well, with dates and places; I believe that would have made the narrative feel even more grounded).
Where it really mattered was when the author attributed thoughts and feelings to Virginia. This didn't work for me because, as the author said, Virginia almost NEVER talked about her work as a spy. She was very private and she didn't like revisiting those parts of her life, either because it was bad memories or she didn't want to take glory for something that wasn't all that glorious. All of the author's information about her was secondhand, which makes sense because Virginia didn't leave much of a paper trail and she's also dead, so she couldn't be interviewed. When you read the acknowledgements, you're led to assume that a lot of the more personal details came from the author's extensive interviews with Virginia's niece. That's totally fine, she's an excellent source of information. I just wish that in the narrative there would have been a little distancing, even something like: "It's likely, based on discussions with her niece, who knew her well, that Virginia [felt/thought/etc.]..." The narrative is currently written as if the author knows, for sure, this is how Virginia was thinking and feeling at that exact moment, as if she had written it in a diary. But she didn't, and in the later chapters, when the niece is specifically mentioned, she says that Virginia almost never talked to her about her work. So why does the author phrase it like that?
It is, admittedly, a very small thing, but I came away with the distinct impression that the author was putting words and feelings into Virginia's mouth. That, combined with the fact that when I closed the book I thought, "Well, that felt very surface-level", made me dock a few stars.
tl;dr: The content is 5 stars, hands down; Virginia Hall is a badass and is one of the reasons why the Allies won WWII. The writing is closer to a 3, because sources weren't integrated, thoughts and feelings were attributed to Hall when we cannot say for certain she felt/thought those things, and it wanted to cover so much information that it never dug deep into certain topics (tactics, how Virginia's set up her contacts besides "talking").