I agree the Amazon API is probably your best bet.

For your consideration, and I'm not saying Amazon is doing this, but I've run into sites that will redirect the request if they can't pass you a cookie or session id and get it back or they see your referer isn't from inside their domain, and you're requesting a secondary-page instead of the main page.

My workaround was to use WWW::Mechanize, because it maintains info for the pages retrieved. It's just a big wrapper for LWP::UserAgent, as is LWP::Simple, only WWW::Mechanize is smarter... or maybe more full-featured. Anyway, it's easy to use too, and probably should be a part of your toolkit.