Reviews on Amazon are becoming attack weapons, intended to sink new books as soon as they are published.

In the biggest, most overt and most successful of these campaigns, a group of Michael Jackson fans used Facebook and Twitter to solicit negative reviews of a new biography of the singer. They bombarded Amazon with dozens of one-star takedowns, succeeded in getting several favorable notices erased and even took credit for Amazon’s briefly removing the book from sale.

“Books used to die by being ignored, but now they can be killed — and perhaps unjustly killed,” said Trevor Pinch, a Cornell sociologist who has studied Amazon reviews. “In theory, a very good book could be killed by a group of people for malicious reasons.”

In “Untouchable: The Strange Life and Tragic Death of Michael Jackson,” Randall Sullivan writes that Jackson’s overuse of plastic surgery reduced his nose to little more than a pair of nostrils and that he died a virgin despite being married twice. These points in particular seem to infuriate the fans.