What do football helmets and laser printers have in common? According to Tenner, they exemplify a new sort of technological backlash that turns the promise of progress on its head. Tenner, a fellow at the Woodrow Wilson Center for Scholars, argues that progress in numerous fields of endeavor has been undercut by unanticipated ``revenge effects,'' which he describes as ``ironic unintended consequences'' of human ingenuity. Examples are myriad: antibiotics that promise the cure of age-old disease but end up breeding resistant microorganisms; imported wildlife that competes too successfully with native species; computer printers that create better-looking documents--and force everyone to desktop-publish memos that would convey the same information if handwritten. The examples are organized under several headings, from medicine and environmental disasters to pests (both animal and vegetable), computerization, and sports (which, interestingly enough, offers some of the best evidence of the thesis). The football helmet, designed to reduce injuries, actually encourages a more violent style of play, creating a new and more serious kind of injury. While Tenner claims to be neither pro- nor anti-technology, he often seems to press his thesis beyond useful limits, as in his observation that those who dwell near wooded areas must now be on guard against tick bites; this is neither a new phenomenon nor an effect of technology. He has clearly done an impressive amount of research, but his footnotes (which attempt to cover whole paragraphs in one sweep) do not let the reader easily follow his research; often an interesting and provocative quote will go unattributed. And a convoluted style often forces a reader to reread an argument that could have been more simply stated. Tenner's subject is undoubtedly interesting, and his examples will strike close to home for many readers; the book would be even better if he had not tried to inflate his useful observations into universal truths.