Harriet M. Welsch would eat Anne of Green Gables for lunch.

Not literally, of course: Anne isn’t a tomato sandwich. But if the two went toe-to-toe in some sort of battle royal for 11-year-olds, Lucy Maud Montgomery’s plucky orphan wouldn’t stand a chance. Unlike Anne — and Pippi Longstocking, and Pollyanna, and countless other cheery kid-lit protagonists — Louise Fitzhugh’s Harriet isn’t friendly or agreeable. She’s rude, impatient, temperamental, arrogant, and sharp, especially when taking vengeance on the classmates who read her meticulously kept notebook.

Harriet is, in short, a jerk — but a smart, perceptive, lovable jerk, one who’s wholly relatable whether you’re 11 or several times that age. When I’m snaking my way through a crowd of cement-footed commuters, I can hear Harriet’s indignant voice whispering in my ear: “Fast. That’s the way I move, fast. What’s wrong with that?” When I surreptitiously write down snippets of strangers’ conversations — what, doesn’t everybody? — I can sense her silent nod of approval.

Harriet’s edge has won her scores of fans, including novelist Jonathan Franzen. “I don’t know of a better novel about the costs and rewards of being a truth teller,” Franzen says in a cover blurb for Harriet the Spy ‘s 50th-anniversary edition , which will be released Feb. 25. “I love the story of Harriet so much I feel as if I lived it.”

I get where he’s coming from. When I first discovered Harriet circa second grade, I had never even heard of her favorite drink (the egg cream) or the contraption she uses to spy on crazy old Mrs. Plumber (a dumbwaiter). She was an only child in 1960s New York; I was the youngest of three in 1990s Pittsburgh. While we both sported glasses, hers were merely cosmetic; she wore them “because she thought they made her look smarter.”

But those surface details hardly mattered. Like Franzen, I identified so fully with Harriet — her emotions, fear of change, frustration, and loneliness — that she instantly felt like an old friend. Inspired by her, I even started keeping a journal in which I carefully wrote mean things about my friends. During a fateful fifth-grade camping trip, that choice came back to bite me…hard. (P.S. Katy, Julia, Whitney, Kate — I’m still sorry.)

Despite that episode, Harriet wasn’t a bad influence. My bond with her was so strong precisely because her faults and virtues mirrored my own. Later incarnations of the character penned by people other than Fitzhugh — the 1996 film that introduced me to fan rage (Ole Golly does not look like Rosie O’Donnell), two wan sequels by Maya Gold, a horrific 2010 TV movie called Harriet the Spy: Blog Wars — fail to capture what made the original so captivating because they turn her into someone the real Harriet would find insipid. Thank heavens, then, for this anniversary edition, which I hope will introduce a new generation to my endearingly jerky little heroine.