my friend (a prof) told me that publishers approach her with new textbooks (the 'new' stuff is really just the changing words, numbers and units on problem sets

my friend (a prof) told me that publishers approach her with new textbooks (the 'new' stuff is really just the changing words, numbers and units on problem sets) ... she ends up using older editions so students can buy used i remember that in almost all of my math courses (esp the graduate courses) i wasn't required to buy books (the prof wrote pdf notes and post in on his site) i find that no-bullshit courses tend to less corrupt