Some books sold on Amazon have DRM and some do not. But "DRM" is not listed anyplace on the book descriptions that I have been able to find. How can I know before I buy an ebook from Amazon if it has DRM?
Books that have "Simultaneous Device Usage: Unlimited" listed under "Product Details" do not have DRM (Digital rights management). Those without this disclaimer have DRM.
Usually we can check a Kindle eBook has DRM or not via its product details. We can tell if a book has DRM protection in 3 cases.
If it says "Simultaneous Device Usage: Unlimited", obviously, the book is DRM free.
If it says nothing, it indicates the book is DRM protected.
If it has a "Simultaneous Device Usage", but it gives a number of licenses, such as "Up to 5 simultaneous devices", then it will have DRM.
You can refer to http://www.epubor.com/how-to-tell-if-an-ebook-has-drm.html