For what it's worth, I have the same issue and have been watching Youtube videos in FF by falling back to the HTTP version. It's not as if the TLS was offering any privacy anyway.
IMO, your book is far too expensive. As a casual interested in dev-ops (surely your target market), I'm completely turned off by you asking old-academia style prices of an ebook. I appreciate you're charging to cover the opportunity cost of your consulting, but presumably you're also aware that pricing it on your perceived value is a suboptimal strategy. Have you considered reducing the price to open up a larger market, and if you have, what is your justification for not doing so?
I'd imagine there were a relatively small number of well-rated suppliers servicing the majority of trade, and fewer still producers. If DPR was in fact taking a ~10% cut, those suppliers would have stood to make considerable sums of money given the profit margins involved.