A recruiter from Amazon emailed me (I didn't apply) to ask me to interview for a role. I never spoke with the recruiter on the phone, but she scheduled 2 phone screens that went well. The phone screens were primarily technical interviews, mixed with some behavioral/history questions. After the 2nd call I didn't hear back for over 2 months. The Monday after the NYT article about working at Amazon dropped I heard back that they "loved me" and wanted to interview me in-person. OK, so I scheduled a day/time. Despite the already scheduled in-person interview, I received emails from 3 people in the recruiting department on the week of my interview asking me to schedule 15 minute calls with them. I got the impression they were all sharing each other's projects and were redoing some of the work others had already done, trying to have identical calls to cover identical topics, but I guess it was good that they just wanted to see if I needed anything.
You can expect to meet with multiple people back-to-back for 6-8 hours. The most important thing for people who want to work at Amazon is that they align their behavioral interview answers to Amazon's guiding principles, this can all be found online and may be mentioned by recruiters. However, over the course of the entire interview process, they are very secretive. They will not tell you what the interview will be about, or even the names of who you will be meeting with.
The interviews are not difficult, they're actually fairly average. The main thing is that you need to be careful about getting tired during the interviews, as you will retell the same stories over and over again to over 5 people. Everyone is heavily cutting up your answers for reveals of any flaws. Personally I was not very interested in Amazon due to the bad reviews, so I did it for more of the experience. A few people I spoke to looked like they worked at least 60 hours a week regularly. I also noticed a few would complain about other people they worked with, and said they would file feedback about these people when they had problems. Although they saw this as a positive thing, I saw it as a negative representation that of people ganging up on each other based on any perceived flaw, not actual flaws. You get the sense speaking to people at Amazon that they are constantly cutting into each other, thinking that they are polishing you into a marbled stone statue, when all they are accomplishing is fragmenting each other. No one I spoke to had worked at the company for more than two years, or looked happy to work there. Also, I was never asked any technical questions about Amazon's services. It looks like knowledge of their products isn't a major requirement depending on the role you're applying to.