Only the ground floor was ever finished.  When I first visited the castle in 1995 that was all you could see.  I went back in 2009 and now they have built out a portion of the second floor into a gift shop and cafe.  It is worth seeing if you ever come to Germany but don;t expect anything but a superficial resemblance to a real castle.  One of the most impressive things in the castle is the King's bed, it supposedly took something like 20,000 man hours to carve and I can believe it.