Eric Larson, Dead Wake: The Last Crossing of the Lusitania (2015).
Another one of those books that reminds us of how hard it can be to act on intelligence which is based on code-breaking. Always the question is “What if we save ____, but lose our ability to read our enemies’ messages?”
In any case, an interesting quick read about events that brought the U.S. into WWI when many wanted us to stay neutral. The most surprising part? That many blamed Captain Turner for being torpedoed!