There is already a sophisticated amazon gem out there called ruby-aaws, but ASIN in comparison is reaaaaaaaaaly easy to use!
It currently just supports the ItemLookup via REST but is easy to extend and understand!
If you want to have a look at the whole Amazon E-Commerce-API go here.
The code currently runs only on Ruby 1.9 due to encoding issues with the Amazon REST output (if YOU know how to backport this, you are welcome!).
require 'asin' include ASIN configure :secret => 'your-secret', :key => 'your-key' item = lookup '1430218150 item.title => Learn Objective-C on the Mac (Learn Series)