There's a wonderful edition, in the original German, published by Macmillan, copyright 1962, in New York, edited by T.C. Dunham and A.S. Wensinger. The edition was meant to be used by students-- it has an English introduction, a glossary of Hindu and Buddhist terms, and a complete vocabulary list-- but Hesse's original text is untouched. I don't know if it's still in print. My copy was printed in 1968 (fifth printing). You might try one of the online rare book searches. I highly recommend this edition to any English-speaking reader who wants to read Siddhartha in German. I'm glad to hear you're planning to read it in German! You'll enjoy it thoroughly, I think, and you may be amazed at how much more subtle and beautiful a book it is in German than in English! Read my post entitled "better in German" for more comments on the subject.