I distinctly remember the author of my Linear Algebra courses textbook was the professor himself. He only assigned homework out of that book and you had to buy

I distinctly remember the author of my Linear Algebra courses textbook was the professor himself. He only assigned homework out of that book and you had to buy the book through his website/preferred publisher. It was not available in print at all so you couldn't even buy it in the bookstore. The cherry on top, was that his book was chock full of errors. We were constantly receiving emails from the professor letting us know which problems HE HAD ASSIGNED had errors and which numbers to change in his own book, etc. How this is allowed to happen is beyond me and was beyond frustrating for all of us as students. Worst experience I ever had with a teacher and textbooks. This wasn't even advanced linear algebra, just the basics. You could literally assign/use any book published in the last 20-30 years and nothing would change about our learning experience. Math doesn't fucking change so often that a new book is needed every 6 months and everybody knows it.