I'm of two minds regarding Sisters of Night and Fog.
On the one hand, this book features the stories of two amazing women: Virginia, an American who, along with her French husband, helps downed Allied airmen reach safety, and Violette, a spitfire British and French citizen who joins the SOE to fight against the Nazis in France. I did not initially know that these were real women, and finding that out halfway through the book did somewhat change my opinion of things. Violette's exploits seemed over-the-top, and I was a bit put off that the author was making her out to be so heroic, but it turns out the real Violette did all those things! It's still a bit crazy, but knowing her actions are factual rather than the result of the author trying to make an overly-capable, overly-brave character helped me to like the story more. Virginia is outstanding in her own right, she just posses a quieter spirit than Violette, and the number of men she was able to help guide to safety is incredible.
The two women's stories are explored in-depth, and this is where my real issue with the book lies. I found the story to be very slow. Yes, there's a lot of danger, and yes, there are plenty of nail-biting moments, but overall, I felt there were many scenes that could've been cut without sacrificing character development. It was easy for me to set down this book, and I didn't feel compelled to keep reading until about three-fourths of the way through the story. Once I discovered that Violette and Virginia were real women, I cheated a bit and looked them up, and knowing their fates made me want to see exactly how the author would handle things. By the time the women found themselves in Ravensbruck, I was glued to the page.
In the end, Sisters of Night and Fog is a fascinating read about two real historical figures who refused to let the Nazis destroy France without putting up a fight. Virginia and Violette had very different personalities, but they both loved their countrymen and their families enough to put their very lives on the line to do what was right. Although the pacing was an issue for me, this is certainly a wonderfully-written novel that will make you cry at the same time that you're cheering on the courage and tenacity of the human spirit.