I think I'm not alone when I say that it took me until 3/4 of the way through this book for it to pick up steam. I listened to the first half on audiobook and was glad to switch to the hardcover, as there were a few things essential to the plot that could not be conveyed in the audio version. It's the story of two women, one a pilot and one a spy, and their unlikely friendship during WWII. I'm glad I finished it, because the ending was masterful - intense, stunning, and ultimately heartbreaking.