The language is not too complicated so the book qualifies as reading stuff for a foreigner wishing to practice his German reading skills. The translation is - judging from my reading experience - well done and worth reading. I think I don't have to tell you anything about the story - see the reviews of the English version for details (besides: who wants to read more about the content of such a book than the back page offers - it would spoil some of the fun since the Potter books are in part a crime story!).
'Harry Potter und die Kammer des Schreckens' is the German translation of the second Harry-Potter-book.