I've been seeing lots of stories in the news recently about how poorly the workers are treated (Allegedly). There's a new book about being an Amazon worker (*in the UK) called Hired, which sheds light on a lot of things. (Allegedly)

https://youtu.be/UIakiR0B-LQ

Haven't read the book yet but watched a few news stories about the topic.
This one alleges that they use temporary workers in order to avoid granting workers any kind of worker rights: https://youtu.be/gYUJjpIxkCU

Lastly a recent piece from Democracy Now:

https://youtu.be/qCtFWob-ho0