I bought three discworld books from itunes last night. I'm listening to #5, Sourcery, today. Part 2 of 3 has at least two skips in it. That is, it jumps from one scene to another, in the middle of a word. So it's definitely an error in the recording/transcoding, and not a feature of the book itself.
So now I get to spend some time attempting to find a way to complain to apple about this, so they can come back and say "nope, the recording is like that, suck it".