If I highlight and annotate in my new and fairly new textbooks, will I be able to sell them back?

If your school is anything like mine they don't give near what the book is worth compared to what they resell it at in the first place. That is if it is in next to new condition. My school would take it for a much reduced price. So basically I would be giving them the book. After a semester ends I go to craigslist.com and go to books a post them there. Local students check there before starting their semester. I get a much fairer price that way and that is selling for about half of what the bookstore would sell a used one for.