Sometimes I feel that professors purposely make errors in their textbooks so that they can print a new edition the next year without having to do any additional writing. Although it is a good way of generating money (or a steady consumer base for a poorly-written textbook that would otherwise go un-purchased), I find it frustrating when I pay $110 for a textbook that has typos riddled through it.
I experienced this with my science for non-majors professor last year. Not only was the cover of her self-authored textbook generated with WordArt, but the images used to illustrate the scientific principles we were supposed to be learning were from ClipArt. To top it all off, prepare yourself, she cited Wikipedia not once, but numerous times as a legitimate source for her findings. Clearly, this woman put a lot of effort into her work and I got the honor of absorbing her poorly-written knowledge for the low, low price of $110. I sucked it up and bought the thing, knowing that I could not pass her course without the book and its accompanying workbook. I eased the pain of the purchase by reminding myself that I could sell it back at the end of the year and recoup some of the expenses. Instead of highlighting key concepts and theories, I spent most of the semester underlying and reporting typos. Finals week came around and I ran to the campus bookstore immediately following my final. But I could not sell it back, oh no. I was informed that it was now considered useless because my professor was releasing a new edition the following semester. Turns out she wrote down every typo I mentioned and popped out a crisp new version. I have decided to never make that mistake again and that is perhaps the only valuable thing I learned from that course.