By ISAAC GUZMAN
Daily News Feature Writer

The happy ending has long been a staple of children's literature. From the Hardy Boys to "The Little Mermaid," the hero may find himself tested but always foils the bad guys or ends up marrying his true love.

The latest literary phenomenon among the junior set, however, has turned that tradition on its head.

The nine books dubbed "Series of Unfortunate Events," written by one Lemony Snicket, present readers with an unceasing onslaught of awful occurrences.

"If you are interested in stories with happy endings, you would be better off reading some other book," writes Snicket in the series opener, "The Bad Beginning." "In this book, not only is there no happy ending, there's no happy beginning and very few happy things in the middle."

But the sad plight of the newly orphaned Baudelaire siblings -- Violet, Klaus and Sunny -- has proven to be catnip for young readers. They can't seem to get enough of the Baudelaires' battle with the nefarious Count Olaf, who seeks to steal their inherited fortune.

On this week's New York Times best-seller list, four "Unfortunate Events" titles are found among the top 10 children's books. In a little more than two years, the series has sold more than 4 million copies. A movie, a musical and four more written installments are also in the works.

Into the Breach Left by 'Harry'

Like many children's books in recent years, their success has been bolstered by the "Harry Potter" phenomenon, says Diane Roback, children's books editor at Publishers Weekly. With several years between the release of each J.K. Rowling title (two of which are on still on The Times' list), children and their parents are looking for something good to read until Harry resurfaces.

Lemony Snicket's alter ego, Daniel Handler, is happy to oblige. But the series' author is interested in more than a fantastic tale. He's trying to usurp the hyperbolically happy tone of some of the books he read as a child.

"I remembered this overwhelmingly moralistic tone in all of my least favorite books," Handler recently said on public radio's "Fresh Air." "So I thought it might be good to mock that from the outset and warn children away from a story. Instead of the sort of typical treacly beginning, which is, 'This is a very charming story and you're just going to love the adorable hero.'"

The Baudelaires are, in fact, relatively adorable heroes. Klaus and Violet are bookish whiz kids while infant Sunny speaks only gibberish.

Utterances such as "Hux!" and "Neepo!" are translated into plainspeak by the author.

How Dark Is Too Dark?

But as the children are drawn into increasingly gothic plots -- which find them falling down elevator shafts and being prepped for unwanted surgery -- the books recall tales straight out of the Brothers Grimm.

While the "Perils of Pauline"-like thrills may draw kids in, child psychologist Paul Rosen says that it may be too much for some children, especially 9- to 10-year-olds who are just beginning to understand the concept of death.

"Children whom I've talked to about these books usually say they're very sad and very scary," says Rosen, author of "TLC: Talking Listening Connecting...With Your Kids." "Pretty much every adult in this book is portrayed as letting these kids down."

Parents, however, seem not to mind scaring the dickens out of their kids. As with the "Harry Potter" books, adults find plenty to admire. Snicket gives older readers a barrage of literary and pop-culture references. He also offers sharp observations about contemporary life. Lawyers, for instance, "make heaps of money" because the books they have to read "are notorious for being very long, very dull and very difficult to read."

"They're sort of the anti-happy books, but they're also elegantly designed and the illustrations have an Edward Gorey-esque feel," says Roback of their adult appeal. "And without alienating kids, they're also hip and ironic. So everybody feels in on the joke."