My high school German has almost completely lapsed, as one would expect with years of minimal practice. I thought this hörbuch would be perfect, since I've read the Hitchhiker's Guide to the Galaxy several times through in English, so I don't get lost even if I can't understand some bits.
The narrator is excellent, doing good dramatized voices that makes it easy to tell who is whom and gives some emotional ambiance for the narration. He speaks at a good normal pace, and sometimes goes a bit fast, but mostly the words don't run together too much. His accent sounds like normal Hochdeutsch, not swiss or austrian, but I can't really tell that well.
I'd recommend this strongly to any Douglas Adams fan who wants to brush up on their German. Even if you're not familiar with the story, I think you'd really enjoy it if you're a little more fleißig than I am. It's a funny and enjoyable story.