honest or just dumb?

I am done with my mini-mester course (which was actually a pretty good course - I learned a lot). However, we did have to buy $140 worth of books. Since this is actually the official first week of summer session I, there was a possiblity that I could return my books and get my money back. But I don't know, I felt a bit dishonest about it. So, now I'm stuck with these two huge reference books of the Aquatic and Wetland Plants of the Southeastern United States. The're actually pretty nice reference books - I'm just unclear as to when I'll need to use them...