Joan Rivers in 2009. After an ill-fated late-night show nearly ruined her career, the comedian worked for years to make a remarkable comeback. (Dan Steinberg/Associated Press)

Sara Eckel is the author of “It’s Not You: 27 (Wrong) Reasons You’re Single. ”

Before Joan Rivers came along, female comedians were essentially cartoon characters: Think Phyllis Diller in her fright wigs and clown makeup, Jo Anne Worley with her crazy laugh and candy-colored boas. Then Rivers stepped up to the mic and in her Brooklyn accent said, “Can we talk?

Here was a comedian we’d never seen before, a woman brazenly talking about being a woman. Few topics were off limits, from sex to housework, childbirth, men and most bracing, herself. Joan Rivers built a career on poking fun at Joan Rivers: “I was so ugly that they sent my picture to Ripley’s Believe It or Not, and he sent it back and said, ‘I don’t believe it,’ ” was among her classic punch lines.

“Last Girl Before Freeway,” Leslie Bennetts’s frank and compelling biography of Rivers, who died in 2014, takes its title from another Rivers joke. “I’m the last single girl in Larchmont,” she said early in her career. “My mother is desperate. She has a sign up: ‘Last Girl Before Freeway.’ ”

Bennetts neither eulogizes nor judges her subject. Instead she allows her copious research — culled from original interviews, comedy documentaries, magazine articles and Rivers’s autobiographies — to tell the story.

"Last Girl Before Freeway: The Life, Loves, Losses, and Liberation of Joan Rivers," by Leslie Bennetts (Little, Brown)

The first half of the book reads like a good potboiler: A young woman, hungry for love and success, sees all her dreams come true after making a powerful ally, Johnny Carson, who introduces her to the world on “The Tonight Show” and subsequently makes her its permanent guest host. Later, Rivers gets the opportunity to make history as television’s first female late-night host on the (then) fledging Fox network.

Then it all goes very wrong. Rivers’s move to Fox infuriates her mentor. He bans her from “The Tonight Show” and never speaks with her again.

In one of the book’s strongest chapters, Bennetts presents the Carson debacle as a mystery, meticulously laying out both sides of the feud and presenting new evidence that a minor player might have been responsible for a rift so bitter it spanned decades: “The Tonight Show” embargo wasn’t lifted until Jimmy Fallon took the chair in 2014.

The downward spiral continued. In large part because of the colossally bad management of Rivers’s husband, Edgar Rosenberg, the Fox show was quickly cancelled. Rosenberg subsequently killed himself, leaving Rivers at age 54 with an empty bank account and a shattered career. After briefly contemplating her own suicide, Rivers instead began one of the most remarkable comebacks in entertainment history.

“What she accomplished over the next quarter of a century would be a stunning achievement for anyone, but for an aging woman in an unforgivingly sexist entertainment industry it was unprecedented,” Bennetts writes.

The second half of the book is devoted to Rivers’s revival, and it starts out strong. Rivers’s decision to sell a product line on QVC is presented not as the act of a bottom-feeding has-been but of an intelligent and determined woman who needed to earn her living. The book exhaustively recounts Rivers’s remarkable work ethic and versatility. Her role in Neil Simon’s play “Broadway Bound” in 1988 garnered her extremely positive — and very surprised — reviews.

Rivers also hosted a daytime talk show and a radio show, wrote and directed a Hollywood film and a Broadway play, and wrote several books. When she took to the Oscars red carpet, she forever changed the fashion industry. (Before Rivers started asking, “Who are you wearing?,” designers focused on dressing supermodels, not actresses.) The year of her 80th birthday, Rivers performed 62 stand-up gigs, shot three different television shows and traveled regularly to Pennsylvania for her QVC appearances, Bennetts reports.

“When Rivers died at eighty-one, she was, improbably and amazingly, at the height of her fame,” Bennetts writes.

While Bennetts, a longtime Vanity Fair writer best known for her 2007 book “The Feminine Mistake,” plainly shows admiration for her subject, the book is no valentine. Instead, it’s a clear-eyed exploration of Rivers’s historical and cultural significance. Quoting Gloria Steinem, Bennetts demonstrates how Rivers was one of feminism’s “transitional” women. On one hand, she was an unapologetic careerist who flagrantly disobeyed the cultural expectation that she aspire to a life of PTA meetings and country-club lunches, instead blazing a path for a generations of female comedians. But she was also traditional enough to give her husband nearly full rein over the business aspects of her career, despite his glaring incompetence.

Rivers’s uneven feminism — and frequently jaw-dropping meanness — is also revealed in her antithetical relationship to beauty. She ridiculed the unrealistic beauty standards women face, but she also obeyed them, subjecting herself to starvation diets and excessive plastic surgery. As her act evolved, she rigorously enforced those strictures, reserving particular scorn for Elizabeth Taylor after the star gained weight. “As her success grew, her perspective began to shift from victim to oppressor,” Bennetts writes.

Bennetts is unflinching and fair, but in the book’s latter half, the sheer volume of dutiful reporting starts to drag down the pace. The chapters on Rivers’s over-the-top decorating style and penchant for hanging out with Upper East Side socialites, while relevant, can’t match the high drama of the Carson fiasco, but they’re given nearly equal weight, stocked with details about her taste in clothing and furniture and encumbered by superfluous quotes. In a chapter chronicling Rivers’s fondness for plastic surgery, seven different friends and associates offer the opinion that she took it too far. Ya think?

Bennetts also relies heavily on the analysis of others. It’s one thing to get numerous quotations from the players behind the scenes at “The Tonight Show” in the 1980s. But when the subject is a contentious episode of “The Celebrity Apprentice,” which anyone can watch, it’s unclear why she offered the insights of a blogger rather than her own. Similarly, instead of providing her take on a controversial 2015 Vanity Fair spread of 10 late-night hosts — all of them men — Bennetts extensively quotes a Huffington Post article.

Nevertheless, Bennetts offers an important work that lifts her much-dismissed subject to her proper place in history. You can love Joan. You can hate Joan. But “Last Girl Before Freeway” won’t let you deny her significance.

The Life, Loves, Losses and Liberation of Joan Rivers

By Leslie Bennetts

Little, Brown. 418 pp. $28