This book, written back in the early 50's, is the tale of HMS Unbroken under Alastair Mars, her captain for a tour in the Med during 1942, the "hinge of fate" in the second world war. It starts out with his travel to Gibraltar, landing Commandoes into Vichy France, and then proceeding to the Malta station during the height of the Siege.
From there, HMS Unbroken goes out on a number of patrols - shelling a railway line or two to disrupt the flow of supplies to Rommel in the Western Desert, sinking a merchantman or two, and damaging couple of Italian heavy cruisers so badly they took no further part in the war. There are also another few occasions where Unbroken is dropping special forces ashore: and the heartbreak of a failed insertion is all too real when things go wrong.
Unbroken is a little 600-ton submarine with a crew of 30-odd men, originally built as a training boat: tiny and fragile by today's standards, and small even by the standards of the 1940's. It is with dark humour we learn that after a heavy depth charging from which she was lucky to survive it is quipped that her name should be changed to "badly bent" or words to that effect.
All up, this is a compelling little read, which takes you under the sea on a series of WWII patrols in a close little boat. You feel every rivet popping, every leak, and the wait for a torpedo to hit its far-off target. There is little of the big picture here, but as a personal memoir of submarine warfare this is one of the best.