Objectively this is a 5 star book, but I gave it 4 stars for personal preference. It was very well-written, beautifully constructed in terms of interweaving plots, jumping between different chronology, incredible characters, and as far as I could tell, historically accurate. I was surprised by the ending-- it continued much longer past the climax and tied up a lot of the loose ends in ways that most novels don't do. The climax of the novel itself was certainly suspenseful, especially after a long, slow buildup to that point. I enjoyed this book, but I took away one star rating because I am simply not a huge fan of historical fiction, and some of the subject matter was a bit heavy for me (nothing major, just in general WWII is not a very happy or light-hearted setting). I recommend this book to people who like high-quality books. And even if you don't usually read historical fiction, I think it's a good book with which to diversify your bookshelf! (I listened to this book as an audiobook, and if you are someone who likes French and German names to be pronounced properly, I strongly advise you to avoid the audio version! Otherwise, the English parts were well-read)