So I was at the mall where I live and found a Borders in it and bought the, The Night Angel Trilogy. When I got home I found out that book one was missing 100 pages. First time I ever bought a book and it was missing pages. I just thought this was kind of odd.
I've actually encountered a similar case. I bought a book for class and it was missing 40-50 pages. I was able to trade it in for a better copy, so that wasn't a problem. You should hopefully be able to get a refund for it, or at least a better copy.
Most bookstores will accpt an obviously defective book for exchange if it looks new and is a title they sell, even without a receipt. They can return a defective copy to the supplier for credit, so its no loss to them, and it's good customer relations.