Via Das Boot I've become fascinated with German's uboat warfare. Even up to a point that I did a presentation on Operation Paukenschlag for my American Studies course in university. I've also watched some good documentaries on German tv. So I now know a bit of what went on but could someone help me on finding a good book that explains more about the various routes the uboats travelled, the tactics, etc.

In short: I'm looking for something of a beginner's guide.

I do have Erminio Bagnasco's "Submarines of World War Two" but found it rather technical.

Are there books you'd recommend for beginners?