Honestly, there is very little that can be done to prevent this type of attack. Your ISP is your best hope in stopping it once it happens. A solid ISP can block any IP that exceeds a set amount of bandwidth. It really isn't that hard to stop once they are aware of it-if they are a "real" ISP.
You are right, in that the ISP is the best line of defense. However, there are things the books/victims can do to to make it harder for the attacker. Both the books and ISPs have to work together.
