One of my professors had a textbook that was shockingly out of date for the subject. Like we’re talking using scientific data from 1995 at the latest, and I took this class 2 years ago. He sent a bunch of emails to the textbook author and eventually he came out with a “Fourth Edition” in response that changed NOTHING. The book was exactly the same except for a different cover. It was so bad that in the syllabus our professor warned us not to buy the fourth edition for the hefty $70 upcharge because it’s the same thing as the third edition.