"U-boats of the Kaiser's Navy", by Gordon Williamson, and illustrated by Ian Palmer, is a short (48 pages) overview of the German submarines and their usage in World War I. The book describes the early development of the U-Boats, to include weapons and powerplants, briefly covers the different types of deployed by the Germans, and gives a short operational summary by year. Probably close to half of the book is taken up by excellent photographs and illustrations.
While providing some detail about the U-Boats, I found the volume too short to provide more than just fairly basic information about the submarines and a very few of their commanders. For example, while the book discusses the various types of U-Boats and the regions they were deployed in, the author never really discusses how they were employed, their strengths and weaknesses in their roles, difficulties they faced, nor provides more than incomplete summaries of their overall success and failures.
I additionally found some nits to pick about his writing and analysis. For example, when discussing the heavy armament carried on many of the U-Boats, he mentions that mounting the heavy armament may seem out of place but points out that the World War I U-Boats didn't have to face the anti-submarine measures of World War II submarines. All well and good up to that point. But in the discussion that follows, he talks about how the deck guns were dangerous to use and became considered superfluous weight and were removed, and how anti-aircraft armament was added in its place. But it's not clear until a bit later that he's actually talking about WW II deck guns, and that deck guns were a very valuable weapon for WW I U-Boats.
Additionally, as another reviewer has also noted, the author claims that the "Uboatwaffe" represented Germany's only real chance to achieve a successful conclusion to the war, when actually, America entered the war as a direct result of Germany initiating unrestricted submarine warfare in 1917. This act alone probably doomed Germany. If the United States had not entered the war, Germany's 1918 offensives stood a much better chance of succeeding, perhaps allowing Germany to at least negotiate a favorable peace, if not win the war outright. So, due to the way they were employed, the U-Boats probably cost Germany the war.
This is not a bad book by any means, but it needs to be longer, and have more analysis and assessments.