David Mamet is a writer who loves paradox. Here's a whole book about acting that tells you almost nothing about how to act; only how not to. Instead, you get Mamet's philosophy of life, a sustained meditation on the bravery needed to get up on a stage and face an audience.

As you would expect from the author of such testosterone-fests as Glengarry Glen Ross, American Buffalo, Oleanna or Wag the Dog, True and False is vigorously aggressive and laddishly unsubtle. It sets its sights on what Mamet dislikes and despises - theatre academics, drama teachers, pretentious directors - and then blazes away. Like a brash hunter, Mamet crashes through the thickets, taking pot shots at anything that moves. Bam! Stanislavsky gets wasted. Bam! Method acting reels from the blast. Bam, bam! The "arc of character" gets both barrels. Down goes "work on the script" - and so does subsidy. Sacred cows gasp their last.

Stanislavsky's a "dilettante" theorist; his method is a "nonsense", a "cult". Actors, argues Mamet, should stay out of acting school. They should forget about investigating their character; they should ditch books about the text. If you want to act, give up study and just go out and do it.

Instead of academies, what you need is courage. "Say the words as simply as possible", with as little interpretation and characterisation as possible. Above all, don't bother with all those "funny voices". Uniquely for an author, Mamet claims that "it doesn't matter how you say the lines". What matters is what you mean. "What comes from the heart goes to the heart."

Such aphorisms are about as far as Mamet goes in telling actors how to do their job; the biggest part of this short tract is about what actors should avoid. Naturally, such heresies are a great read. Mamet knows his profession and how to annoy it. And, like many of his own characters, he is provocative, insistent, cruel, amusing and way out of order.

Anyone who loves theatre will be excited by Mamet's passionate advocacy, even if appalled by his unreasonableness. But his point is that acting is not about being "genteel": "Actors used to be buried at a crossroads with a stake through the heart". Theatre is a deranged carnival; so break the rules, free yourselves from dogma.

Guru or charlatan? Sometimes, it just ain't clear. True and False is the kind of book that, when you throw it across the room in irritation, comes bouncing back into your hand. Like a drunk who buttonholes you in a bar, Mamet won't let go until he's told you what the world is really, really all about.

This book is bound to exasperate drama teachers and infuriate the theatre establishment (especially in the US), but it will also inspire and torment many a young hopeful. As the man says, "it is not a sign of ignorance not to know the answers. But there is great merit in facing the questions".