Where are best deals on rn books?

A lot of people have recommended www.half.com to me.

or amazon.com. I'm doing my RN-BSN right now and OU and find most of my books there. Usually, I have to go to the college bookstore to find the ISBN numbers so i can look them up online. I'm sorry but I'm not paying 180 bucks for a book when I can get it online for half that.

That's what I did when I was in school and then turned around and sold the one's I knew I wouldn't use again and got my money back, if not more.