Yeah Mastering Bio is kind of an additional thing to the textbook but it's designed to be used alongside Campbell (still this doesn't mean Campbell is a 100% must get, though, so you could just purchase the access code). As for all this other stuff, just wait for your first lecture for every course when they'll tell you about textbooks unless it's specifically said tha a book is compulsory, in which case you can get it beforehand. It's also helpful to ask others who've done the course about whether textbooks are needed. Co-op should be a last resort since it's expensive, and the 'prescribed by your lecturer' I don't remember seeing since I didn't go online to browse for books, but I'm assuming you can just ignore it for now. If they want latest edition, they will probably tell you first lecture about why - it could be that the order of things have been shuffled around so if they want to put textbook page references it's easier if everyone has the same edition, or it could be because something's been tweaked or added or blah blah blah. If the reason isn't really major then I don't see why you can't get an older edition, and if they don't tell you why then you either don't get the book or if you're super paranoid and have a lot of money to spare or if you know it'll help then go for the latest edition. Again, don't be too trigger happy re: textbooks since you won't need most of them.