I think the reason they don't warn you about DRM is because almost every ebook from most sellers has DRM and they assume you either already know or, if you're new, you're buying a book for a device registered to their books.
My guess is that all but 13 or 14 people in the world already know about DRM and now that you do that's even further reduced.
If you bought the book from Amazon for a non-Kindle app or device they make it real simple to return the book for a refund within 7 days of purchase. If you bought it from someone else you might give them a call and explain to them. You might or might not get a refund.
If you want more information you probably should give us more information. What device do you want to use to read the book? Where did you buy it? If that device is the correct device is it registered to the correct account?
Barry