In 1973, Jessica Mitford was offered the post of distinguished professor for the autumn term at San José State University in California. (This despite, like all her sisters, never having even attended elementary school, let alone university.) One wonders if there are any of the senior staff still alive who shudder to recollect all the trouble she caused there; there are certainly going to be alumni who will remember her with deep affection and respect. The problem, you see, and you'll read all about it here, was that among the requirements conditional to her taking up the post was that she take an oath of loyalty and provide the university with a set of her fingerprints.

Soon enough, San José found itself up to the neck in the mulligatawny, as Mitford implacably opposed both measures, rousing almost the entire student body to her defence and giving the administration no end of a headache. Why, she asked reasonably, should she swear to uphold the Constitution of California, which runs to three hefty volumes? "Do I uphold and defend, for example, Article 4, Section 25 3/4, limiting boxing and wrestling matches to 15 rounds? I don't know. Perhaps it should be 14, or 16?" And so on. The brouhaha made national news. "I was, I must confess, enjoying every minute of this enormously."

For my part, I can't remember when I enjoyed a collection of journalism so much, or laughed out loud so often. Sometimes the laughter is tinged with darkness. On a tour of the southern states of the US, she meets a school board member who says: "It don't seem possible no Nigra could have an IQ of 150, do it, now?" Her response, of course, is: "To me it do . . ."

Spirited, extremely witty and sharp and, perhaps most importantly, driven by a powerful sense of social justice, Mitford was, quite simply, one of the most useful journalists of the 20th century. That she could also make you laugh while exposing the shenanigans of the corrupt, or, as she preferred to call it, muckraking, makes this book indispensable.

It is also useful as, and intended to be useful as, a manual for doing the kind of journalism she did. She is very interested in inspiring people to continue the tradition of muckraking, and just because the technology of journalism has changed, it doesn't mean that techniques of getting interviewees to spill beans they would otherwise have preferred unspilled have changed, too. So as well as comments, or post-mortems, on every piece here, there is also an entertaining and helpful introduction in which she goes through the basics of her trade, scattering tips and wisdom ("Unfortunately, ethics is not one of my strong points . . ."). This is a function of her politics, obviously: she wants to help everyone up the ladder, not pull it up after her, which is why she was so particularly aggrieved by the Famous Writers School, a correspondence course which sold the gullible the expensive promise of making a living from writing. (How the columnist and publisher Bennet Cerf was ever able to appear in public after the skewering he gets here is something of a mystery.)

And you can learn so much from her style, too. She opens the book by quoting Nicholas Tomalin's celebrated formula for real journalistic success  "ratlike cunning, a plausible manner, and a little literary ability"  but her literary ability is far from little. She always knew just how much pressure to apply, like a skilled executioner. "'When are you going to get angry?' a friend asked after reading a draft of my article about the Famous Writers. Never, I answered; it is not in my sweet nature to lose my temper, especially in print."

Although, it has to be said, there would be many at the receiving end of her attention who would dispute that line about her sweet nature. But then it was always her business to afflict the comfortable and comfort the afflicted. Never mind if you haven't read any of her more substantial works (The American Way of Death, Kind and Unusual Punishment); here, in essence, is her achievement.