NEW YORK — From the nibs of his ink pen to the spirit of his rhyme on the very first page, John Bemelmans Marciano has tried to stay true to a grandfather he never met in putting out the first all-new "Madeline" adventure in nearly 50 years.

Since 1939, generations have cherished the old house in Paris covered in vines and the 12 little girls in two straight lines, including the smallest one with a can-do streak and a penchant for calamity.

But why tamper with a character so endearing?

"I had always thought, 'Boy, it's never going to go away,' but classics do fade," said the 38-year-old Marciano, who lives in Brooklyn and spent years studying the drawing technique of his grandfather, Ludwig Bemelmans, for his "Madeline and the Cats of Rome."

Marciano, who's touring the country promoting the recent release, is far from a newbie children's writer, with three books on other subjects to his credit. In fact, he's not even a newbie "Madeline" purveyor.

While sifting through Ludwig's personal papers for his acclaimed tribute book about his grandfather's life and work, Marciano discovered unfinished text and pencil drawings that led him to illustrate and complete the story for "Madeline in America" in 1999. He also turned Madeline into a good-etiquette advocate in "Madeline Says Merci" and created a rhyming board book featuring the spunky French redhead in "Madeline Loves Animals."

But "Madeline and the Cats of Rome" is the first full-length story book using the character. In it, Marciano sends teacher Ms. Clavel and the girls on vacation. Once in Rome, there's petty crime, a curly-haired antagonist turned do-gooder and a creaky old house full of cats.

Early reviews have been mixed. Some librarians, parents and young fans are happy for a new tale about the convent schoolgirl, but some critics are aghast at the quality of the work.

"Awkward syntax and forced rhymes abound," wrote Publishers Weekly. "The joy and brio of the original books go missing."

No matter, Marciano is busy signing books for "Madeline" fans. Over the summer, he rode with the mayor of Decatur, Ga., in an all-Madeline children's costume parade that kicked off the town's book festival.

Madeline merch still sells, though Marciano said his family is struggling to regain rights to some of it. And he's not the first literary offspring to carry on a family legacy. Laurent de Brunhoff, 83, has written and illustrated more than 30 "Babar" books since the elephant character's creator, dad Jean de Brunhoff, died in 1937.

Other relatives wrote under their own names after the death of their proficient loved ones. Some beloved characters and book series, including "Curious George" and the "Wizard of Oz," were continued by writers outside the family.

Leonard S. Marcus, a children's book critic and historian, said letting a favorite - and lucrative - cast of characters die with its creator is a hard decision for relatives and publishing houses alike.

"I don't think it's very good," Marcus said of the new "Madeline" book. "I think the story is confusing and the art is not as graceful and funny. The drawings feel a little weighted down and leaden to me. There's a lot of skill there, but I really don't know why people just don't do their own work instead of imitating somebody else."

The new book, the first full-length Madeline story since Ludwig's "Madeline in London" in 1961, has a prominent shelf spot in one of Manhattan's top children's bookstores despite grumbling that the rhymes are off and the story fractured.

"Some people are never going to like it," Marciano said of stepping into his grandfather's ink-splattered shoes.

"I certainly have ambivalent feelings, to some extent, about it," he said. "The one thing, though, is that people love the books. My doing new books doesn't in any way detract from the original five that my grandfather did."