ONDON, Jan. 4 ó Lynne Truss was on her way to deliver a lecture at the British Library recently when she was reminded yet again that a tremendous gap exists between her natural obsessions and those of other people.

"Punctuation," Ms. Truss replied, when her taxi driver asked what she planned to talk about. But the word didn't compute; he heard something less weird in his head. "Ooh, in that case," he replied, "I better get you there on time!"

So it has been a shock to the rarefied system of Ms. Truss, 48, that her book "Eats, Shoots & Leaves: The Zero Tolerance Approach to Punctuation," has become this year's surprise No. 1 best seller here. Among the legions of the surprised are the executives at her publishing house, Profile Books, who ordered a modest initial printing of 15,000 books, but now have 510,000 in print; and Ms. Truss's friends and family.

"When I was writing it, everybody thought it was commercial suicide to spend any time at all ó even just four or five months ó on it because obviously it wouldn't sell," Ms. Truss said in an interview. "My mother said, `You have to get a sticker printed on the front that says, "For the select few." ' "

There are many possible reasons for the tremendous success of "Eats, Shoots & Leaves," a spritely volume that leads the reader through the valley of the shadow of comma splice; refers to the apostrophe as "our long-suffering little friend"; makes a rousing case for the semicolon's usefulness in, among other things, "calling a bunch of brawling commas to attention"; and describes Woodrow Wilson's inexplicable visceral hatred of the hyphen, which he called ó spectacularly undermining his own argument ó "the most un-American thing in the world."

It could be that the book is this year's intellectual stocking-stuffer, the perfect novelty gift for the chronically hard-to-amuse, akin to last year's "Schott's Miscellany" or, from 1996, "Longitude."

It could be that bookstore browsers have been drawn in by the book's cheerful yellow cover, with its droll illustration of a panda earnestly painting over the comma in the title, a visual reference to a panda-based joke about punctuation mishaps.

Or maybe Ms. Truss has indeed touched a nerve of latent pedantry in a world in which, as she writes, increasing numbers of people "don't know their apostrophe from their elbow."

"It's as though one's pointed out that the sky's turned a different color and everyone thinks, `Yes, I've noticed that,' " Ms. Truss said, seeking to explain the book's success. "It's triggered a lot of people's imaginations, really. I hope they're not going to go around interfering with other people's punctuation in a horrible way. But they've become aware that punctuation is quite a good system for making yourself clear, and that it's been completely neglected by so many people."

It has been a heady time, Ms. Truss said, speaking by telephone from her house in Brighton. She has been interviewed across the British news media, and what she thought would be a slight, Christmas-y volume has been scrutinized up and down by reviewers, who have been mostly delighted, and occasionally jealous.

"Eats, Shoots & Leaves" has been sold with great fanfare to the United States, where it will be published by Gotham Books in April. Suddenly, people who once treated Ms. Truss like a nitpicking fussbudget are taking her seriously.

Ms. Truss has always been a whisperer, not a shouter. Much as she is aggrieved to the point of physical distress when she sees a sign advertising "carrot's" for sale, she is not one to cause a scene. "I think most of the people who care about these things are not confrontational people," she said.

But she has had her moments. Writing an article about apostrophe abuse for The Daily Telegraph last spring, for instance, Ms. Truss held aloft a six-inch apostrophe on a stick in Leicester Square, strategically placing it so that the offensively titled Hugh Grant film "Two Weeks Notice" became, for a short, giddy interval, "Two Weeks' Notice." But what was most striking was how few people took her point.

"Most everyone walking past sort of shrugged and gave the usual `get a life' kind of response, which I find so tedious," Ms. Truss said. "It's very belittling. It's obvious that one doesn't only care about apostrophes."

Pedants may be born, or they may be made, but Ms. Truss ó who prefers "stickler," if pressed ó has been one for a long time. After graduating with an English degree from University College London, which for reasons of its own has no comma in its name, she began work as a copy editor at Radio Times magazine. A series of editing jobs followed at a variety of arts magazines. Ms. Truss then became a television reviewer for The Times of London; covered sports from the point of view of "someone who could take a very uninformed view," she said; and finally became a freelancer.

She has published three comic novels, all of which have sold, Ms. Truss says, "nothing." (Translation: maybe several thousand copies apiece.) She has also written a number of plays, some of them set in ancient Rome, for Radio 4, the BBC radio's highbrow arts channel. "Eats, Shoots & Leaves," which in the spectrum of such books is more playful than "The Elements of Style" and less prescriptive than The New York Times Manual of Style and Usage, came out of a series Ms. Truss did on punctuation for Radio 4 some months ago.

The book is dedicated to "the memory of the striking Bolshevik printers of St. Petersburg," who, Ms. Truss writes, "in 1905 demanded to be paid the same rate for punctuation marks as for letters, and thereby directly precipitated the first Russian Revolution." As for its title, it comes from a joke that begins, "A panda walks into a cafe."

The panda orders a sandwich, eats it and then fires a gun into the air. On his way out, he tosses a badly punctuated wildlife manual at the confused bartender and directs him to the entry marked "Panda."

Whereupon the bartender reads: "Panda. Large black-and-white bearlike mammal, native to China. Eats, shoots and leaves."