Although the library is still in development, it already provides support for the vast majority of the AWS v3.1 API. For example, all forms of product search are implemented, along with the transaction details API and the remote shopping-cart API.
Ruby/Amazon also offers advanced features not directly available via the AWS API, such as the ability to retrieve all results pages for a particular search, rather than having to deal with AWS responses of 10 results per page. Ruby/Amazon will even use parallel threads to improve the performance of such multi-page searches.
Another advanced feature is the ability to cache responses returned by AWS. If the cache is used (as it is by default), the results of each unique query will be cached and used for 24 hours. The cache can be manually flushed of all or just the expired entries.
One other useful advanced feature is the ability to determine the appropriate Amazon locale for a client, based on its IP address or hostname. This allows you to direct AWS operations to be performed within the correct geographical Amazon site for the given client. German clients can be made to operate within amazon.de, British clients sent to amazon.co.uk, etc.
More features are planned for future versions, such as Amazon Web Services for Sellers. See the TODO file included with the software.
The easiest way to get started is to click on the Amazon class and to follow the examples.