The story of the only U-boat to serve in the Royal Navy is fictionalised in this short book from James Follett. A new, inexperienced crew take U-570 (the true name of the vessel was initially concealed by Follett to protect survivors) to war. It is a tough time for the Kriegsmarine, with lots of famous boats being sunk, and U-570 is thrust into the maelstrom.
Weaved into the story, are references to Ian Fleming when he worked for naval intelligence (I could have done without the references to the Bond books), a POW camp in Northern England and a few minor characters. The second half seems more fiction than fact, but overall an enjoyable enough short read.