Like other O'Reily Hacks books I have read, Amazon Hacks is interesting, but inconsistent. A lot of the book is dedicated to introducing Amazon's features and exploring the available services. Of course there are some real hacks, clever ways to repurpose the site, that are the namesake of the book.
As a manual for Amazon, the book is useful. It covers many interesting features of the site, and does it in an easy to read manner. I don't know much about other available resources, but if you want to know Amazon well, this book is a good starting point.
As a hacks book, it didn't amazed me. There are both neat ideas, and
interesting code listings. But nothing that made me say
great! Additionally, most of the book's more powerful hacks are based
around generating custom URLs, submitting your own web forms to Amazon
targets, and screen scraping. Normally there isn't anything wrong with
these approaches, but they seem inappropriate when there is a Web Services
API available. The final chapter is focused on the API, but I think it
should have been used in hacks throughout the book. Using the API
exclusively in a standalone chapter at the end of the book gives it the
status of an afterthought, instead of a core focus. Still, the example code
for interacting with Amazon is instructive.
If you want to learn a lot about what the Amazon website offers, this book has some good information. As well, if you are writing software that might benefit from Amazon's product database, or might make you some money using the affiliate program, or might take advantage of one of the many other Amazon features, this book could be useful. (Though if you do write software that leverages Amazon, please take my advice and go straight to the API. Don't bother with screen scraping.) However, if you are looking for amazing new ways to use the Amazon site, or hope to find inspiration for creating a clever hack of your own, this book probably doesn't have what you are looking for.