Otto Giese had an unusual war. He was a merchant marine officer with a German cruise company when the shooting started in 1939, and the cruise ship he was on was in the Caribbean. His ship attempted to return to Germany, but was intercepted by the Royal Navy and scuttled by its crew. They wound up being interned by the U.S. Navy (entering the U.S. through Ellis Island!) and found their way to San Francisco and then Japan with the idea of being repatriated to Germany through the U.S.S.R. Instead, though, Giese wound up as a watch officer on board a blockade runner which successfully made the run from Japan to occupied France via Cape Horn, rendevousing with a German commerce raider in mid-Pacific along the way.
Once he was back in Germany, he sought out service in the Navy, in spite of opposition from his employer. He wound up serving as an enlisted man on U-405 through four patrols operating out of Norway against Murmansk convoys. Then he was transferred to officer training, and soon assigned to U-181, which travelled from France to the Indian Ocean via the Cape of Good Hope. Once there, they eventually landed at Penang in Malaysia, intending to restock with supplies needed in Germany and return there later. When they tried to sail back home, the sub's drive bearings failed and they had to return to Indonesia, where they waited out the end of the war. He then spent some time interned by the Japanese in Malaysia, more time as a POW both there and in Britain, before finally returning to Germany. He eventually settled in Florida and became a U.S. citizen.
This book comprises what is described as a "war diary" kept by Giese. This stretches credulity a bit, and I think it would be better to describe it as a memoir. The author recounts the events briefly, and some of the chapters are so short it only takes a few moments to read them. Sinking of Allied ships is handled in a sentence, perhaps two. There isn't that much information on life on a U-boat during WW2.
Why then the high rating? Turns out Giese was a shutterbug (camera enthusiast) and kept a Leica camera with him at all times. He managed to develop photos of his experiences and keep them safe all these years, and the book is sprinkled with more than a hundred of them. Frankly, the pictures are much better than the book is, and I enjoyed them a great deal. The book was still good, don't get me wrong, but without the photos would have drawn three stars, not four.