If students buy used books, they aren’t buying new ones. Most fields don’t change fast enough that a two-year-old book is hopelessly out of date. At least, the introductory course material is relatively stable. You probably will be fine using a previous edition, especially if you hit the library once in a while and grab the current edition from the reserve desk to make sure you’re not missing anything important.

But one of the tricks the publishers use is to change the page numbering to make it tricky to keep up with assignments that use page numbers unless you buy the latest. So check with your teacher. (She’s very likely sympathetic to your desire to save money, by the way.) Ollie