"It is an entirely harmless book — as all books are."
Hey, you're an idiot!
About the quiz with the list of words, one thing they all have in common is that each of them contains a smaller word within it without having to rearrange letters (and not counting one-letter words). E.g. 'reign' inside 'foreign.' You have to take 'bi' as a word within 'big' for that to work, but I think that's OK.
Who knows whether that's what DFW had in mind, of course.