I was never too keen on this story. It was good enough I guess but it made very little sense. It seemed like there was a potentially very good story in there trying to get out, but not enough room for it within the confines of the two episodes. It has probably benefitted a great deal from being fleshed out in the book.
It is definitely one to check out; it is
radically different in scope and motive to the original episode. I often find that the classic novels quite often 'tidy up' little plot holes and oversights that were present in the actual stories - never is this more apparent than in this novelisation!