Quite simply, you can request the removal of an inappropriate review on Amazon by sending an e-mail to firstname.lastname@example.org. In the email you should provide
1) The book title and (if you have it) ISBN
2) The name used by the reviewer
3) The first sentence of the review, and
4) The date it was posted.
State why you believe the review to be inappropriate, and you should receive a reply back from Amazon in a number of days.
Before contacting Amazon, here are a few details about Amazon's approach to inappropriate reviews that might help you out further.
1) Amazon is well known for removing reviews and often for reasons that seem totally mysterious, especially to those that have posted the review
2) Amazon is known for deleting negative reviews posted by competing authors
3) They will remove reviews containing inaccurate information about the author or containing comments that have nothing to do with the book.
4) Reviews written by people impersonating others will be removed
5) Reviews that contain profanities, spiteful intentions, or political bias are not allowed.
6) Reviews that solicit votes or some sort of self- advertising for the reviewer will also be removed.
7) Amazon also prohibits the inclusion of phone numbers, email addresses, or URLS, or pricing information, and alternative shipping or purchasing methods.
8) Amazon deletes reviews considered to be "illegal, obscene, threatening, defamatory, invasive of privacy, infringing of intellectual property rights, or otherwise injurious to third parties." And it does not accept "political campaigning, commercial solicitation, chain letters, mass mailings, or any form of 'spam.'"
In other words, if you prompt Amazon to remove a review that contains any of the above characteristics, they are more likely to do so. Amazon does monitor book reviews but it than gratefully accepts other vigilant eyes such as from yourself, and a score of community groups that help report abuses. As Amazon reviews can be posted anonymously, they cannot always stop malicious or ridiculous reviews being published.
So if you see anything that applies to any of the above rules, do send a request to review the review, especially if it is about your book, or a book you like.