I worked there 2004–2007. I had a great time and I learned a lot. If you like the team that made you an offer, and you're excited about what you'd be working on there, then go for it.
A few things I've written about what Amazon is like:
https://www.quora.com/What-are-some-cultural-faux-pas-when-w...
https://www.quora.com/What-allows-Amazon-to-be-so-innovative...