Liest du Harry Potter und der Stein der Weisen hörbuch?
Is this course sufficient for understanding Harry Potter und der Stein der Weisen? What about Die Unendliche Geschichte?
Well, I believe audiobooks are listened not read :-)
As for being able to listen any audiobook after finishing the german tree here, I wouldn't recommend it as a first thing to do. It might be very frustrating. Try some shorter podcasts, try to read some websites (wikipedia, news), later on maybe part of a book (or a whole one if it can keep your interest). Watching TV shows and movies would be a great help. After all this (and I mean after at least few hundred hours of doing all that) you might be able to comfortably listen to an audiobook. The disadvantage of audiobooks is that you don't see the sentences (like in normal book) nor do you see what's going on on the scene (like in a movie or TV show). So you are left blind. Listening to a new language requires a lot of practice, you might know the words / vocabulary but you have to learn to pick them up by just hearing them which is much harder than seeing them on paper.