It's authored by Eberhard Rossler and published by the Naval Institute Press, I don't know if it's still available I have had my copy for several years now. Much of my comment to the Types shortcomings from Head valve freezing on the snorkles, poor battery well circulation and poor quality workmanship are all explained in great detail as well as the post War interest and development of the type by allied Navies.
I think Freidman's books are all great but this particular book gets into the nuts and bolts of German Submarine design and deployment. It also has nice plans and maps of all the major U Boat bases etc. Info on every Boat in the German Navy from Baur's Boat in the 1850s to the latest U Boat types in German Service. A great de bunker for sure.