Depressing in the sense that it tells you a lot of things about what you're eating and how food arrives at your table that while important, you'd rather not know. It's also expansive, meticulously researched and engrossing. It manages to take a subject that doesn't, at least to me, sound interesting, and turn it into a page turner.

The book begins with the infancy of the industry, and how it went on to change America's social and geographical landscape. How fast food started in California, where kids would drive to restaurants and hang out in their cars, and how the drive for efficiency led to technological innovations that de-skilled the workplace and standardised food delivery. It follows the rise of a few companies on the back of identikit outlets that sprang up along highways across the car crazy United States and turned all the towns into the image of each other. It also tracks how individual ranchers were driven out of the game by a few huge corporations who fixed prices and sliced up the industry for themselves.

Schlosser spends a lot of time dealing with the "founding fathers" of the industry. This is the most fascinating part of the book, a study of the characters that gave birth to the fast food cause. Ray Kroc, the force behind the growth of McDonald's, was the most fanatical. He convinced the McDonald's brothers to sell him the franchise rights for the chain, and made millions. Today the McDonald's company's profits from food sales are dwarfed by the income that comes from leasing the ground that franchisers operate on. Kroc's philosophy was simple: It is ridiculous to call this an industry. It's not. This is rat eat rat, dog eat dog. I'll kill 'em, and I'm going to kill 'em before they kill me. You're talking about the American way of survival of the fittest, he told a reporter in 1972.

The men lead into the politics, and the book explores the power the major players exert in Washington through donations and lobbying, and how the parties have let them get so strong. The cynicism of the fast food boards, their influence in keeping the minimum wage so low (in real terms dropping since 1968), and their hatred of regulation are all laid bare. The author particularly targets Republican administrations: "It is a sad but undeniable fact that for the past two decades the right wing of the Republican Party has worked closely with the fast food industry and the meatpacking industry to oppose food safety laws, worker safety laws, and increases in the minimum wage. It is this cosiness that Schlosser blames for the worst aspects of the industry.

The book then moves on to food supply and delivery. It is graphic in its depiction of the rearing and slaughter of cattle, poultry and pigs. The author watches the mechanised, production line carnage while wading knee deep in blood. There are detailed, but never voyeuristic, descriptions of the maimings and deaths at the loosely-regulated American factories that befall the illiterate, illegal immigrant workers manning the crushers and wielding the skinning knives. The author argues these are not really accidents because the major meatpackers know it happens routinely but do nothing to stop it. One major company was convicted of keeping two injury logs, one for inspection and one for its own files. Some factory owners force their workers to sign waivers giving up their rights to sue for compensation, and even to basic worker's comp, a right given to every working man. The choice is left to the workers to take a gamble that the company will pay for their treatment or sue them in a case that the company's lawyers can drag out for years.

He then focuses on the conditions for the workers in the restaurants, a life of abuse, injuries and real danger. In 1998, more restaurant workers were killed on the job than policemen, often by current or former employees turned to robbery.

Schlosser also records the fallibility of the production process. How cattle will be incorrectly stunned and cut up while fully conscious. The process itself is very difficult to do right. The butchery of the animals results in a huge amount of waste and this contaminates the meat. Almost every hamburger you have ever eaten will have contained faeces.

After all the description of the savagery of the industry, Schlosser ends on, from his perspective at least, an upbeat note. He believes that the saturation of the marketplace will severely curtail the power of the fast food barons. The year 2000 was the first year when the food industry gained no new customers. Wall Street is getting edgy. "A two per cent decline in sales is enough to send their stock prices spiralling downward"the glory days of the major chains seem to be over," Schlosser writes.

Reduced profits could be the only thing that changes Big Food's behaviour. That could be good news for the rest of us. As for me, I don't really care. I'll still have that hamburger.