I recognize your two categories of bad math books and would like to add a third: commercial textbook publishers "padding" the pages with filler. It seems every book made for first-year undergraduate students is 10x thicker than it needs to be: there are these huge color images and lots of repetition, which makes students just tired and not want to read the book.

It's completely artificial padding and unnecessary: you can teach calculus in 100 pages, you don't need 1000 pages (cf. Silvanus Thompson book on calculus or my books). I think the padding is done to make the exorbitant price tags seem more reasonable, so this is why I'm optimistic about this book since it's coming from the Eastern Block (no padding).