First of all, did you register the copyright of your book? If so, you gan go after statutary damages (aka big bucks) without having to prove that you have lost any money on the deal. If not, the most you can claim is actual damages, which would amount to the money you would have made if you had sold those books rather than him. That's probably not worth it.
The best you can do in that case is file a DMCA claim with his ISP - they will probably have a page somewhere telling you how to do this, if not, google the requirements for a DMCA claim - and that will get his site taken down. In the mean time register the copyright, so if the guy pops up on a new web site you can go after statutary damages.