Why was playwright John Osborne an angry young man? The tag stuck because he personified a generation of dramatists who detonated the understated drawing room dramas of Terrence Rattigan and Noel Coward that dominated London’s West End at the time. Imagine a theater without the rawness of Eugene O’Neill, the bold experimentation of Elmer Rice, the steamy subversion of Tennessee Williams, and the demotic tragedies of Arthur Miller. That was English drama before Osborne exploded the London stage in 1957 with “Look Back in Anger.”

Osborne’s overstatements, his long speeches (so reminiscent of O’Neill), his strident anti-classstructure themes — his sheer emotivism — shocked audiences, critics, and fellow playwrights. Terence Rattigan said Osborne’s plays were chaotic. Laurence Olivier deemed them a disgrace to the nation. Of 12 opening-night critics, only two recognized the breakthrough “Look Back in Anger” represented.

The play’s producer thought it would close unless the Sunday newspaper critics published raves. In fact, two critics did just that, with the legendary Kenneth Tynan almost single-handedly turning critical opinion on its head by heralding the birth of a theatrical genius. When an excerpt from the play was broadcast on television, Osborne attracted the young audience he craved.

Two years later, Olivier would be playing the seedy Archie Rice in Osborne’s second masterpiece, “The Entertainer,” which the master actor considered one of his favorite roles. In “Inadmissible Evidence,” a searing dissection of his protagonist’s inability to deal any better with success than with failure, Osborne produced a third masterpiece. The author of two brilliant autobiographies as well, he emerges from John Heilpern’s masterful biography as a giant of modern literature.

When reviewers say a biography reads like a novel, they usually mean it has a fluent style, such that the biographer has created characters, scenes, and even dialogue that are true and also riveting. Well, “John Osborne: The Many Lives of the Angry Young Man” (Knopf, 544 pages, $35), is all that and more.

I cannot recall reading a biography that was so amusing and intense. In part, of course, the reason is that Osborne was both wickedly funny and savagely sad. A big-time nurser of grudges — he thought the year his mother died a good one — he was also hilarious about his own appalling flaws.

Nevertheless, biographers have been known to make exciting subjects dull. Not Mr. Heilpern, who writes with enviable ease and wit. Even more astonishing is the way he presents himself as a character without becoming obtrusive. He starts his book by explaining how he came to write Osborne’s authorized biography: getting to know Osborne’s last wife and meeting casually with the playwright long before a biography was in the offing. Thus Mr. Heilpern vividly immerses us in the world that gave rise to this biography.

Even better, Mr. Heilpern brings us along to his interviews. Among his best encounters is with Arnold Running, who gave Osborne one of his first jobs in journalism. Running, at the time 29, was a literary type Osborne associated with his dad, who had died of tuberculosis at 39 when Osborne was only 10 years old. The elder Osborne became a sort of saint in his son’s memory for introducing him to a love of literature and writing.

Running ran a trade journal, the Miller, which published articles about the milling process and windmills. Osborne, who never went to college, drew close to Running, who was writing a novel. Enter the biographer, 50 years later: “Arnold Running was almost 80 when I met him at his home in Brampton just outside Toronto, and still a fine-looking man with his full head of hair and grey beard hinting at the bohemian.” The vestiges of what Osborne saw in Running, a man who may have been obliged to run technical pieces in his paper but who gave promise of something more, are evident in Mr. Heilpern’s pinpoint prose. Running remembers Osborne’s fixation on words, which he would copy daily out of the office’s giant encyclopedic dictionary. For Osborne this was a lifelong habit.

The comedy comes in when Running mentions meeting Osborne’s second wife (Osborne had five in all), the spectacularly beautiful actress Mary Ure. Running’s wife interrupts his account:

I couldn’t see it. She had a moustache.

She didn’t, Arnold.

It is of course too early to start naming the best biographies of 2007, but I can’t help myself. If there is going to be a better-written, more entertaining, or more sharply observed performance this year, I’ll be mighty surprised.

crollyson@nysun.com