I'm not aware of that book, but looking at a summary, you could be right. However, when you pick a topic to write about that someone has addressed before, it's quite likely that you'll explore the same themes. For example, I once came up with an idea for a time travel story about a man from our future going back to the time of Jesus to see what really happened. When he got there he realised Jesus didn't exist and therefore, to make sure he didn't change history, he had to become Jesus and go through the whole thing. I was telling someone about this and they said that they had already read that book. It turns out that Michael Moorcock had written a book called Behold The Man that was very similar to my idea. I had never read the book, but because the themes were so similar, had I written the book, I'd have been accused of stealing the idea. I guess there are only so many stories in the world.
Having said all that, Terry definitely used other writer's ideas as satire. The Colour of Magic, for example, is full of nods to other writers and their worlds.
