“I broke this rule because I developed some of the code while I was a Visiting Scientist at Google, so I followed the Google style guide, which deviates from PEP 8 in a few places. Once I got used to Google style, I found that I liked it. And at this point, it would be too much trouble to change.”

Why would you write a book that targets the Python community and ignore PEP8 styling, inconveniencing an entire community, simply because it would be too much trouble for you to change?

“Also on the topic of style, I write “Bayes’s theorem” with an s after the apostrophe, which is preferred in some style guides and deprecated in others.”

It is deprecated in all modern style guides and should not be used. You’ll get dinged in college English and writing classes for using this outdated and redundant style.

I’m sure this book is great, but, as a point of constructive criticism, I would suggest the author do a better job at adhering to the styles of code and English expected by his target audience, rather than what is comfortable for him.