Reply #22: All literary works are protected by copyright

[Ms. Toad]

and that includes the book reviews (and posts on this site, for what it is worth).

The copyright comes into existence the moment the person who creates the work puts it in tangible form (including a website post That means the visitor who wrote and posted the review owns the copyright at the time they posted it (or earlier if they created a draft somewhere else first).

Amazon requires when you post a review that you grant them non-exclusive rights to exercise the copyrights ("If you do post content or submit material, and unless we indicate otherwise, you grant Amazon a nonexclusive, royalty-free, perpetual, irrevocable, and fully sublicensable right to use, reproduce, modify, adapt, publish, translate, create derivative works from, distribute, and display such content throughout the world in any media" (That list of things you are letting them do is the formal list of copyrights. Because it is non-exclusive, that means you still own it, post the identical review on other sites, let others exercise the copyrights, or prohibit others from exercising the copyrights.

Owning a copyright does mean you have the right to dictate who displays, copies, or modifies it (see the full list above). Enforcing those rights is a little more complex - you actually have to register your copyright with the copyright office before going to court - and when you register it dictates how hard you will have to work to prove how much you have been harmed by someone ignoring your rights.