Easily Abbey's most famous fiction work, the novel concerns the use of sabotage to protest environmentally damaging activities in the American Southwest, and was so influential that the term "monkeywrench" has come to mean, besides sabotage and damage to machines, any violence, sabotage, activism, law-making, or law-breaking to preserve wilderness, wild spaces and ecosystems. It is the bible of what some critics call "eco terrorists".
The book's four main characters are ecologically-minded misfits — a Jack Mormon river guide, a surgeon, his young assistant, and a rather eccentric Green Beret Vietnam veteran, George Hayduke. Together, though not always working as a tightly-knit team, they form the titular group dedicated to the destruction of what they see as the system that pollutes and destroys their environments, the American West. As their attacks on deserted bulldozers and trains continue, the law closes in.
The book was praised for its erudition, flair, down-home wit, and the accuracy of its descriptions of life away from civilization. (Abbey made the West his home and was a skilled outdoorsman.)
Interestingly from a 21st-century viewpoint, the Gang in some ways bears little resemblance to the modern media's portrayal of environmentalists — they eat lots of red meat, own firearms, drink beer (and litter the roadside with empty cans), drive big cars, etc. (Abbey's habits were reportedly similar.) Also, Abbey's politics are not "bleeding heart" (as most of the characters dismiss liberalism): they attack Indians as well as whites for their consumerism, hold little regard for the Sierra Club, etc.
The Gang sees the 'enemy' as those who would develop the American Southwest: despoiling the land, befouling the air, and destroying Nature and the sacred purity of Abbey's desert world. The greatest hatred is focused on the Glen Canyon Dam, a monolithic edifice of concrete that dams a beautiful, wild river, and which the monkeywrenchers seek to destroy. Indeed, one of the book's most memorable scenes is that of Abbey's character Seldom Seen Smith, as he kneels atop the dam praying for a "pre-cision earthquake" to remove the "temporary plug" of the Colorado River.