A book that teaches kids not to use their hard-earned vocabulary because it might make stupid people feel stupid.

You could have a 45,000-word vocabulary and still be virtually incomprehensible if you don't know how to match your communications to your intended audience. Understanding where your readers/listeners are *and meeting them there* is absolutely key to being broadly understood.

Have you ever read XKCD or what if?

My 8 year old didn't feel that way. He loved both books.

What’s interesting about Up Goer Five is how hard it is to explain *and understand* things using only the 1000 most common words! That’s a *tiny* vocabulary.

Gotta say, that has not been my experience.

"If you can't explain something in simple terms, you don't understand it." - Richard Feynman

Being able to meet people at the level of knowledge or vocabulary they’re at is a useful skill. If the goal is effective communication, shared vocabulary is more important than “hard-earned vocabulary”. If that’s not the goal, it’s just intellectual masturbation using an audience.