Flyvpn has a free VPN solution. Your connection only lasts for 20 minutes, but it's more than enough time to buy your books from a 20 minute "vacation" in the US.
I don't feel one bit like a crook when doing this. I have "visited" US almost every week since I discovered flyvpn, and it saves me $2 pr. book since Amazon charges for delivery of e-books to Europe, but I don't think that I'll get to hell for this (at least not only this). Since I started using VPN, these letters from Amazon stopped coming. Proxy was not enough to bypass the system, but VPN does the trick