According to journalist Margaret Croyden, Peter Brook -- that British master of the theatrical cutting edge -- is as imaginatively restless as ever. Brook, the subject of Croyden's newly published Conversations with Peter Brook, 1970-2000 (Faber and Faber, 302 pp., $20.00), recently turned 78, an age at which he might be expected to slow down. On the contrary, Brook still sheds his artistic skin at frequent intervals, looking for fresh challenges in wildly disparate projects. From Paris, where he oversees the International Centre of Theatre Research and mounts new works in his home venue, Les Bouffes du Nord, Brook and his international company of actors, technicians, and writers make periodic forays to work in distant places. Over the years, the company's destinations have included Iran, Afghanistan, Africa, Yugoslavia, Japan, and, of course, the United States (where the Brooklyn Academy of Music is practically a home away from home). Wherever Brook roams, his accomplishments defy our era's disdain for live theater, demonstrating that -- in the proper hands -- stagecraft can still command a spot at the heart of cultural discourse.

Margaret Croyden, whom Clive Barnes calls "America's leading writer on the theatrical avant-garde," first encountered Brook almost 40 years ago and has been writing about him ever since. She is proud to recount that she was introduced to Brook by no less a figure than Polish iconoclast Jerzy Grotowski. The usually tough-skinned journalist writes that, over the years, Brook has been not only a focus of professional inquiry for her but also "a dear friend, a mentor, and a guide -- a truly uncommon human being, and...a consummate artist."

In 1974, Croyden published seminal discussions of both Brook and Grotowski in Lunatics, Lovers and Poets: The Contemporary Experimental Theatre. Her analysis of Brook's work was based, in large part, on a series of interviews she conducted with the director beginning in 1970, when the fanciful Midsummer Night's Dream that he staged for the Royal Shakespeare Company was the toast of London. In the decades since her book appeared, Croyden has continued interviewing Brook, contributing articles on his projects to the New York Times and American Theater Magazine. Now she has gathered her interviews (as opposed to the essays she published previously) into a meaty volume, Conversations with Peter Brook, 1970-2000.

If Croyden's long chapter on Brook in Lunatics, Lovers and Poets may be seen as an introduction to the director's artistry, her new book is the advanced course. Croyden has appended a "selected chronology" of the director's projects to Conversations but she clearly expects her readers to be familiar already with the director's history. Her desire to let Brook speak for himself in Conversations is commendable, but the details of his beginnings bear repeating. The son of a Russian-Jewish émigré, Brook grew up in a bourgeois, intellectual household in London. His first love was movies and, as an undergraduate, he founded the Oxford University Film Society. Although Brook has worked intermittently as a film director, the happenstance of early success in commercial theater and opera transformed him into a man of the stage.

In one of his "conversations" with Croyden, Brook remarks that, over the years, he has invested his creative energies in "contradictory forms" of stagecraft. As a young man, he directed classics of European and British theatrical literature in the English provinces. He undertook frivolous situation comedies in the West End; staged Miller's Death of a Salesman in Brussels, and Williams's Cat on a Hot Tin Roof in Paris; helmed the Lunts' farewell to Broadway; and worked for David Merrick on Irma la Douce and Saint Subber on House of Flowers. He became co-director of the Royal Shakespeare Company, made television programs and feature films, and took on opera at Covent Garden and the Met.

Twelve major Brook projects are dealt with in Croyden's book. First comes the eye-opening A Midsummer Night's Dream, with actors performing acrobatic stunts in a brightly-lit, white box to the atonal accompaniment of guitars, bongos, and tubular bells. The book concludes 30 years and 300 pages later with Brook's speed-demon Tragedy of Hamlet (two hours and 20 minutes without intermission). In between, Brook and Croyden talk about such diverse endeavors as The Conference of the Birds, developed as part of the company's arduous sojourn in Africa; the intense Tragédie de Carmen, which attempted to transport elements of Mérimée's original novel into Bizet's familiar opera; the Indian epic Mahabharata, arguably Brook's masterpiece; and The Man Who, an adaptation of case studies published by Oliver Sacks.

The "conversations" cover a vast array of topics relating to actors and acting, literary and non-literary theater, film, spirituality, and -- dearest to Brook's heart -- Shakespeare and Elizabethan drama. Brook is at ease discussing practical aspects of the theater but he shies away from anything theoretical. At Croyden's urging, he reluctantly explains the radical experimentation (or theatrical "research") that has occupied his energies since, in middle age, he abandoned his lucrative career as a director-for-hire in commercial theater. "I have rigorously avoided applying to the theater anybody else's discoveries," he tells Croyden in an undated interview. "But what I've been very, very conscious of is that discoveries that I've made quite simply through working are the discoveries of certain basic patterns and principle in human beings and in human relations."

Brook is at his most engaging when he talks about the dynamics of the rehearsal hall. "An actor needs a director...to force what won't happen by itself," he says. "The director needs the challenge of actors to bring out what the director can do. It's in this way that the work I'm looking for is always based on two elements: the inner riches of a human group with its impulses, and the call coming from the outside, which is either the material or direction, but something has to be put into the challenge."

Croyden, who taught in the New Jersey university system, is now retired but never retiring; anyone who has encountered her in print or in person knows that she's a cataract of tart critical responses. On New York Theatre Wire (www.nytheatre-wire.com), where she's a columnist, Croyden recently dismissed the work of Styne, Sondheim, and Laurents in Gypsy as neither "engaging" nor "important"; Bernadette Peters as "not really a good actress"; Sam Mendes as "an overrated British director"; and Mary Zimmerman's Notebooks of Leonardo Da Vinci as "not only incomprehensible but exceedingly tedious." One might expect Croyden to ride roughshod over the polite, reflective Peter Brook but, instead, her relentless intensity and hauteur keep the director focused on the questions posed. Again and again in Conversations, Croyden squelches tangents and challenges vague responses, demanding specificity, amplification, and greater clarity.

For all its riches, Conversations with Peter Brook ignores significant chapters of the director's career. For instance, his groundbreaking presentation of Peter Weiss's The Persecution and Assassination of Jean-Paul Marat as Performed by the Inmates of the Asylum of Charenton under the Direction of the Marquis de Sade -- the accomplishment that made Brook a household name -- is hardly discussed. True, that 1965 production falls outside the chronology of Croyden's book, but it was such a landmark in the English-speaking theater that one might anticipate seeing its shadow fall more frequently across this exploration of Brook's later career. Two sections of Conversations -- a chapter on the motion picture Meetings with Remarkable Men in which Croyden quizzes Brook about his aspirations as a filmmaker, and another in which the director talks about the interaction of performers and audience being central to his "research" -- are missed opportunities for exploring why Brook chose to adapt his staging of Marat/Sade, with its crucial breach of the fourth wall, to a medium -- i.e., film -- in which there can be no "real time" interplay between audience and artists.

Among Brook's endeavors within the decades specifically covered by the book, Croyden's most mysterious omission is the funny, existentialist Cherry Orchard which, in its 1988 New York incarnation, featured Brook's wife, Natasha Perry, and Brian Dennehy in a memorable balancing act as (respectively) Lyubov, the bankrupt aristocrat, and Lopakhin, the arriviste who acquires her family estate at auction. Still and all, the true measure of a volume such this one is not its specific content but its success at conveying the authentic voice of its subject. In this regard Croyden's Conversations rates high marks.

For Brook, the theater is the most serious business imaginable; he believes that it "correspond[s] to a psychic need in man." It's his view that, if theater "isn't something that people in a community demand, that people feel they can't live without, without which people would feel deprived, as if you took the sunshine away -- if theater doesn't evoke that same need, it is not a real theater. It's an interesting theater; it's amusing, like a show, a film that you'll go see, or not; it is not for you or against you; but it doesn't correspond to a deep need." Conversations with Peter Brook is a handbook for those who share Brook's conviction that theater is indispensable.