The book begins okay but not spectacularly, but it slowly begins picking up steam, and after a while you realize you're reading a seriously good book. That moment occurs when the plot, interesting enough by itself, becomes tangled in the larger machinations of WWII going on, which at first was just background noise for the characters but then is thrust into the foreground. Without going into specifics since I don't want to spoil the book for anyone, there's a "Holy shit" moment when you realize the characters are about to be trapped when something unexpected happens in the war, and you know this from history, but they of course have no idea what's about to happen.