I remember playing this first on a 48K Spectrum and the 3D effects seemed really good for the time.
Playing it on the ST was better with more colour and faster game play, but by then there were other better alternatives.
Well, VulgarMike, Castle Master certainly isn't as groundbreaking and accomplished as Dungeon Master was, but still it's a very good game. Anyway it isn't a role playing game, so comparing it with DM is quite useless. This is a 3D (first person view) adventure/action game. The graphics are quite poor, but the 3D animation is good. The sounds are acceptable. Technically this is no masterpiece, but the overall atmosphere is really good, and the riddles you have to solve are interesting. It is definitely worth a try. And the soundtrack music at the beginning is one of the best is know.