..The evolution and technical history of German submarines, by Eberhard Rossler. Just got this today from my book club. Only had a quick flick through so far, but if you interested in all the technical specs of U-boats, and their construction, it looks just the thing. It covers the period from 1914 to 1974 and includes plans of many of the bost types, as well as drawings of the construction yards in Germany. Any one else seen this one, it was originally published in German in 1974, then in English in 81.