In a nutshell, 'review-bombing' is a book review left on a book from a reader who often hasn't read it or is someone that disagrees with the message/theme/politics/etc. of the work. Review-bombing can be compared to swarming. It's not a mature look at the writing, plot, and structure--it's about the reviewer and not the product reviewed. To "bomb" means that many target the same book with negative feedback to deter others from buying the book or to teach a 'lesson' to the author that powerful forces are at work.
