Some of the all time greats of mathematics (e.g. Euler) also wrote high school/undergraduate college level textbooks. Now, they're written by corporations that are heavy on graphic design talent and light on mathematical acuteness.
FWIW, mathematics textbooks are hardly the only, or even necessarily even the worst, offenders. They are less prone to outright snafus than science textbooks, and more resistant to the latest educational politics trends than the social sciences and humanities. One of the more depressing gafs from the middle of the source post is this one:
When I point out critical errors in content to a developer’s project manager, there’s generally a pause at the other end of the phone. I’m ruining their day, handing them a problem they don’t want, can’t possibly address given their resources and time. Some do their best; they’ll ask me to make corrections and bump up my rate a bit. Some will ask me to make notes so that they can fix the errors and do the rewrites themselves on their own time. Others will simply sigh, “The publisher knows it’s bad. Just do the best you can.” The publisher knows it’s bad. And yet, it doesn’t seem to matter. That’s because the sales and marketing team is already at work developing videos, brochures, webinars, catalog copy, and whatever else their bloated budgets will allow in order to sell what doesn’t actually exist—a quality product. . . .
A more recent math project I was hired to edit was not only full of content errors, the books were so peculiar in the execution of math concepts and instruction that I hadn’t seen anything like it in all my 20+ years of experience. I asked the project manager if she’d ever seen math approached in this manner. She gave a resigned groan and said no, but this was what the publisher wanted. The books in question were a series of supplemental products designed for struggling students, which is sadly ironic because students of all abilities will indeed struggle to complete the lessons in these books. How could this happen, you might ask? Well, the books were published by a company that was reorganized a few years ago in order to boost profits. That’s when the bulk of the product development staff was let go and the budget for their department slashed. Meanwhile, the marketing and sales departments swelled, as did their budgets. And though many of those in charge now have lofty MBAs, few have little, if any, experience in publishing of any kind, never taught in a classroom, and haven’t the first clue of how to build a coherent educational book from start to finish. The lust for the bottom line—that is how this happens.
It sounds so much like the worst parts of my stint in for profit higher education its cringeworthy. Textbook writing is right up there on the list of activities that big, for profit businesses do poorly.
It is a bit odd really, considering that on the whole, books have not been at the epicenter of areas where capitalism and copyright have just stopped working the way they are supposed to work. Book publishers look superficially like their in the land of peaches and honey compared to record companies and movie studios to hear the folks in the respective industries talk, without actually confirming the facts (although retail book stores are in a rather less blissful state).
One of the big trends in math textbook writing, that I see in the Denver Public Schools curriculum is the dreadful trend of fragmentary cycling - spreading out a topic over a tiny part of the year over many yeras (with lots of repetition) rather than doing a whole subject, mastering it effeciently, and then moving on to something else that builds on it. (And then, there is the dreaded "lattice method"!) There is also way too much teaching down to grade level standards rather than pushing kids, and way too much of a learn a year, recover a year, learn a year pattern.
It is possible to write good textbooks. I still have my wonderful high school geometry textbook, the first that I tought myself from, ignoring what was going on in class. But, somehow, as the author of the linked posts note, you have to develop a purchasing end of the system that rewards excellence rather than mediocrity. Maybe we need to migrate to the system that is in place in higher education, where individual teachers are trusted to pick their own textbooks and text book companies court them relentlessly. Somehow, I'm not hopeful on that score.