Why am I watching a documentary about Joan Rivers?

I wonder this for about five seconds into “A Piece of Work” before dissolving with helpless, falling-over hysteria as Rivers mutters angrily about her crappy stand-up venue and calls her daughter a delicious, three-word insult (go see it!) for turning down a $500,000 offer from Playboy magazine. It’s hard to breathe for the next 84 minutes, not only because Rivers is so unexpectedly hilarious, but also because she’s so shrewd and gutsy in a comedy landscape where execs and audiences expect women to be dimwitted and women are glad to oblige.

Unexpectedly? Yes. I fling myself down in apology for that. It was as a “plastic surgery freak who’s past due” (says her manager) that I and most people know of Rivers. She was a red carpet mainstay whose face was as loud as her voice. “A Piece of Work” takes the audience into the effort behind her continuing quest to remain seen and heard in a world of has-beens and never-wases, and not without

acknowledging the absurdities of money (“Staff, I’m lonely. Who’s going to fuck me tonight?” she jokes) and the fickleness of her business (winning “Celebrity Apprentice” helps the movie escape a

possibly Norma Desmond-like ending). It’s hard not to be in awe of her toughness, fearlessness and especially her approach to the appropriateness of comedy, which can be summed up in one word: always. (This is also a woman who sorts out her troubles with her daughter in a nearly documentary made-for-TV-movie. Hey, whatever works for you.)

An early monologue punchline: “It’s a rough business, so I just want you to know that my name is Joan Rivers, and I put out.”

“You’re going into places you shouldn’t go,” an adviser warned her, to, thankfully, zero effect. She continued to go there. Ferinstance: “No man has ever put his hand up a woman’s skirt looking for a library card.”

How does this 77-year-old grandmother so outdo other female comedians a third of her age? (Come on, name five you actually like. Olivia Munn, for the love of all that is holy, does NOT count.) Some of it is talent. More of it is working on that talent. She’s furious, relentless and uncensored (“[Trick or treaters] say, “I don’t like apples!’ I say, “Well fine! Just eat the razor blade!’) She’s not ungrateful, but she refuses to be complacent. Yes, she’ll do the red carpet stuff. She’ll sell jewelry. It’s work. But she’d rather be on stage, even if it is a lonely and fervently disrespected sisterhood off stage (she names Kathy Griffin, Sarah Silverman, Tina Fey and Lynne Koplitz as other success stories, and only Fey is considered appropriate for polite people to enjoy.)

What’s so impressive about Rivers is her decades of trying to tear down the barriers and her doggedness in the pursuit of comedy and work. She flips through a blank appointment book, early on. “That’s fear,” she says, a fighter eager to get back into the ring. She understands it’s not really a tragedy that the on-stage stool at a low-rent laugh club is being held together with duct tape; it would be a tragedy if there were no audience watching her mock it.

Ashley O’Dell reviews movies that aren’t in the theater anymore and writes truly unfunny one-liners on Twitter. She lives in North Hollywood, near the In-N-Out Burger.