I can't tell if you're joking, but I purchased a math text book as an undergrad that I needed last-minute as a Kindle ebook and it was an awful mistake, in part

I can't tell if you're joking, but I purchased a math text book as an undergrad that I needed last-minute as a Kindle ebook and it was an awful mistake, in part because of text reflow. You'd see a formula at the top of a page but days later when you went back to look for it it would now be at the bottom because the text had reflowed. It really threw things off. There were other problems: the index was garbled and useless (it still had the page numbers of the paper book in it and the formatting was completely off), the text could be resized but the formulas were rasterized and did not scale with the text and were frankly hideous. This was form a major publisher. I'd much rather have had a PDF. But for novels, changing font size and hence reflow of text are super nice.