I'd Add Dr. Seuss to the List of Exceptions.

Fiction Rule of Thumb

The unseen title tag to this XKCD comic reads, "Except for anything by Lewis Carroll or Tolkien, you get five made-up words per story. I'm looking at you, Anathem."

Thanks to Joe for sharing!

Comments

I'll give Tanuja Desai Hidier a free pass, too. (She uses a lot of onomatoepeia-ic adjectives/made up slang, and I found it immersive as opposed to obnoxious.)

It's so funny you mention her, I was just about to pull Born Confused for a book display!

Some folks do the word-coining thing very well. I just read How to Ditch Your Fairy, and there was lots of made-up slang in there, but it was very clear from context what the words meant.

I hate to read a book where I'm constantly tripping over long names, though. If I can't pronounce it by the third try, forget it!