Opening with a made-up quote (that is very simple to Google, which quickly confirms its apocryphal nature) doesn't inspire confidence in the factual accuracy of the remainder of the book...
This level of nit-picking is disheartening...
> "If you can't explain it simply, you don't understand it well enough." - Albert Einstein
Which is listed at https://en.wikiquote.org/wiki/Albert_Einstein#Misattributed
> "If you can't explain it simply, you don't understand it well enough."
Which TFA (and others) misattribute to Einstein