Two main rounds. First was a one hour interview with behavioral questions, followed by a coding exercise. Second was the same thing, except a full day.
Recruiting was a headache. They sometimes take days to respond (sometimes more than a week), so you have to follow up. They also don't always communicate. One of my interviews had to be rescheduled, but they failed to communicate that to me, so after some unnecessary circles, I had to reschedule it for another day. Very inconvenient.
The actual interviews were ok at best. Some interviewers had very strong accents, which made them hard to understand at times. Nothing against people with accents, but they probably shouldn't be conducting interviews. Plus some interviews started late. You can't expect a candidate to be on time when the interviewer is not.
Lastly, Amazon has a policy of not providing feedback to candidates after interviews. I find that unfair given how much time a typical candidate has to put in to preparing for the multiple interviews. But then on top of that, Amazon actually asks candidates for feedback on their interview experience. Double standard much? Google has an equally rigorous interview process, but at least they show some respect to candidates and provide feedback.