Forty years ago, William Goldman pulled back the curtain farther than most of Broadway could have imagined — or wanted — in his delectable book “The Season.” Mr. Goldman had no qualms about eviscerating such golden boys as Harold Pinter and Mike Nichols as he profiled every Broadway entry, along with a few that never made it to New York, from the 1967–68 season.

Dori Berinstein, herself a Tony Award-winning producer, has taken a far gentler survey of a more recent season in her invigorating primer “Show Business: The Road to Broadway.” Her insider credentials may have something to do with the film’s upbeat tone, which often threatens to slide into boosterism, but they also afford a remarkably comprehensive glimpse into today’s high-stakes world of playmaking.

Ms. Berinstein gained a staggering level of access into just about every aspect of the Broadway business during the 2003–04 season — dressing rooms and rehearsal studios, naturally, but also marketing meetings and pit orchestras and even a quick visit inside the half-price TKTS booth. We see Patrick Stewart affixing fake age spots on his head as part of his costume for “The Caretaker,” critics gathering to compare notes, and various musicals participating in the Gypsy Robe ceremony, a silly but charming ritual honoring each show’s most seasoned chorus member.

While she shot footage of every major Broadway production, Ms. Berinstein zeros in almost entirely on four major musicals: “Caroline, or Change,” an ambitious coming-of-age tale set in civil rights-era Louisiana and based on Tony Kushner’s childhood, which was loved by the critics but not the ticket-buying public; “Wicked,” a megalithic retelling of “The Wizard of Oz” from the wicked witch’s point of view, which was loved by the public but not the critics; “Avenue Q,” a racy update of “Sesame Street”-style children’s television, which was loved by both, and “Taboo,” a Boy George biography produced by Rosie O’Donnell, which was loved by neither.

“Avenue Q” gets the most attention, in part because of its universal appeal and in part because the young and self-deprecating creators make for great protagonists. (A home-movie clip shows Jeff Marx, half of the songwriting team, singing “That’s Entertainment” as a tuxedoed 13-year-old.) Ms. Berinstein also plays up the human-interest angle by profiling Tonya Pinkins, who was cast in the title role of “Caroline” less than a year after being on welfare, and the young “Taboo” star Euan Morton. Meanwhile, “Caroline” librettist Mr. Kushner — the most quotable theater artist since the days of Moss Hart and George S. Kaufman — gets about three minutes of screen time.

Some roads to Broadway receive more attention than others. The out-of-town tryout for “Wicked” is discussed, along with a London production of “Taboo,” but nowhere is it mentioned that the other two shows transferred from major off-Broadway theaters – “Avenue Q” from the Vineyard and “Caroline” from the Public. Ms. Berinstein seems loath to acknowledge just how indispensable the nonprofit off-Broadway scene has become within the Broadway business model.

Just like any competition-based documentary these days (“Mad Hot Ballroom,” “Spellbound,” “Air Guitar Nation”), “Show Business” culminates with the big contest that separates the winners and losers. Several theater professionals make it clear that the Tony Award for Best Musical represents the only real hope of viability for an adventurous show such as “Caroline, or Change,” and so the Tonys loom as a glamorous gauntlet. Much is made of how a Best Actress win would mean vindication for Ms. Pinkins, and Ms. Berinstein continues the “Avenue Q”-as-underdog theme: Mr. Marx cuts himself shaving before putting on his tuxedo, and the puppeteers’ limousine is prevented from stopping at the red carpet.

Although her affection toward the “Q” kids and Ms. Pinkins is apparent, she makes no attempt to demonize the hugely popular “Wicked.” The closest thing to a villain is New York Post gossip columnist Michael Riedel, who is seen gleefully predicting doom for each and every show under discussion. He was certainly correct about “Taboo,” and his columns are featured prominently in a montage of the poisonous press that the show received during previews. Boy George calls him a “weasel” and expresses amazement that Mr. Riedel showed up at the opening-night party. (I saw Boy George take the invective a step further late in the run of “Taboo,” when he literally stopped the show and called him a far naughtier word, one the Brits use more freely.)

Even William Goldman, no more a member of Broadway’s inner circle now than he was 40 years ago, is familiar with Mr. Riedel’s column. Mr. Goldman, you may recall, coined the oft-cited Hollywood aphorism “Nobody knows anything.” What Ms. Berinstein demonstrates with infectiously breezy authority is that just about everybody on Broadway knows one or two things. When a lot of those somebodies assemble what they know, sometimes they get a Brit-pop train wreck that loses $10 million. And sometimes they get an out-of-left-field puppet show that wins three Tony Awards. That’s “Show Business.”