I was curious about this novelisation as its by Phillip Hinchcliffe; who produced one of the best periods of Doctor Who history; especially as this was a story from a very different era. However - as perhaps expected by the era that this was novelised - this isn't massively different from the TV story.

The writing itself is a very good description of the TV story - although that means that there's not much reason to read this on top of the TV story. There are a few moments when the writing explains a few differential things and a few times where Hinchcliffe went slightly off script (mostly to add to the intrigue of the story - especially the section when they are in the mountains) but not a lot. This contrasts with some elements that don't translate as well to the written page - in particular the hunt for the first key where the TV show gets over the idea that the others are brainwashed while Barbara isn't in a much greater way than this story initially (where it looks like she's the one in the wrong initially).

On the whole; worth a look if you enjoy the TV story but not remarkably different to it.