For an unfinished story, it's amazing how many versions of "Shada" there are. There was the VHS release with Tom Baker narration summarizing what happened in the unfilmed portions; there was the fully dramatized flash-animated web production that turned it into an 8th-Doctor adventure; there's the audio-only release of same with additional material; and now there's the novelization.
And lets not forget Dirk Gently's Holistic Detective Agency
, which recycled the character of Professor Chronitis. Oh, and the official BBC DVD that's supposed to come out within the next year.
For a lost story that's really just a typical run-of-the-mill Tom Baker story (imho), it's really been done to death.