He created stories about a little boy named Harold who drew whole worlds with his purple crayon. She also wrote classic stories for children, such as "A Hole Is to Dig," and helped spark the career of acclaimed children's book creator Maurice Sendak.

Together, the husband-and-wife team packed quite a punch in the world of children's books in the 1940s through the 1960s, as Philip Nel details in his new book, "Crockett Johnson and Ruth Krauss: How an Unlikely Couple Found Love, Dodged the FBI, and Transformed Children's Literature" (University Press of Mississippi, $40).

"Between them, they created more than 75 books, many of which became classics," Mr. Nel writes. "Five of Johnson's seven books about Harold and his purple crayon have remained in print for more than 50 years, and the series has inspired many other books and authors.

"Where Johnson's feeling for a child's creativity emerged in his artist hero, Ruth Krauss conveyed her respect by bringing real children's voices into her work and in so doing changed the way authors write for young people."

Mr. Nel, director of Kansas State University's Program on Children's Literature, spent more than a decade doing research for this book. Despite its catchy subtitle, however, it's unlikely that his book will ever be a best-seller because of its sometimes-overwhelming detail about people who may only be of interest to children's book lovers.

But children's book aficionados will find that Mr. Nel's book offers a fascinating glimpse into the lives of two hugely creative people whose artistic endeavors actually extended far beyond children's books. Toward the end of his life, for example, Johnson won acclaim as an artist for his paintings focused on math theorems, while Krauss also was known for her experimental poetry for adults.

These days, though, it's Johnson's children's book legacy -- via "Harold and the Purple Crayon" and its sequels -- that still strongly endures. Krauss' status as one of the best-known children's picture-book writers of her day seems to have faded over time, although many of her books remain in print, including "The Carrot Seed," for which Johnson did the illustrations.

Both Johnson and Krauss owe a great debt to Ursula Nordstrom, the legendary Harper & Row (now HarperCollins) children's book editor. In fact, because of the force of her personality, Nordstrom nearly steals the spotlight at times in Mr. Nel's book. (Question: When will someone -- please! -- write a biography of Nordstrom?)

Known for her quick wit, sardonic humor and nearly unparalleled ability to spot talented children's book creators, Nordstrom played a major role in the professional lives of both Johnson and Krauss, cajoling them to produce their best work and fiercely defending their books from critics.

It was Nordstrom, for example, who paired Sendak, then an unknown artist, with Krauss for the now-classic picture book "A Hole Is to Dig." Thus began a close artistic partnership between Krauss, Johnson and Sendak, who considered the couple his alternate parents.

Mr. Nel's biography of Krauss and Johnson is presented chronologically, and he highlights how different their backgrounds were: "She was a secular Jew from a bourgeois Baltimore family; the son of two immigrants, he was a lapsed Methodist who grew up in Queens."

After a somewhat slow start, things really pick up in Mr. Nel's book when Johnson and Krauss, both divorced from their first spouses, are introduced to each other at a party.

As he writes: "He was tall and taciturn. Seven inches shorter, she was slim, exuberant and ready to speak her mind. Her exuberance drew him out of his natural reticence and into conversation. His calm, grounded personality balanced her turbulent energy. They were complementary opposites who felt an immediate attraction toward one another. As Ruth liked to say: 'We met, and that was it!' "

Early in his career, Johnson gained fame as the creator of a nationally syndicated comic strip called "Barnaby," which depicts the adventures of a young boy -- who looks a lot like Harold -- and his fairy godfather, Mr. O'Malley. Once a hugely popular comic strip, whose fans included columnist Dorothy Parker, jazz great Duke Ellington and actor W.C. Fields, "Barnaby" now has been all but forgotten, except by comics aficionados.

(Note: Fantagraphics, a comics publisher, will release a volume of "Barnaby" strips in November. Titled "Barnaby, Vol. 1," the book will sell for $35.)

Krauss, meanwhile, was a free spirit whose own childlike sense of wonder and curiosity made her a natural writer for young children. Like Margaret Wise Brown, author of the iconic "Goodnight Moon," Krauss was a proponent of books that reflected the real thoughts, words and world of children, as opposed to fairy tales and other fantasy books popular with many at the time.

Krauss' work thus was controversial with many librarians, especially the powerful Anne Carroll Moore, head of the children's department at the New York Public Library. They especially objected to the unfettered freedom that children enjoyed in many of her books, such as "A Very Special House," "The Backward Day" and "I Want to Paint My Bathroom Blue."

Both Krauss and Johnson leaned left politically, and Mr. Nel carefully details how the FBI spent five years in the '50s keeping tabs on them before deciding to give up the investigation. Mr. Nel's discussion of the investigation, threaded through several chapters, brings home to readers the paranoia of that period of American history.

Johnson died of lung cancer at the age of 68 in 1975, and Krauss died at the age of 91 in 1993. Yet they continue to touch the lives of children through their books. As Mr. Nel writes: "Whenever children and grown-ups seek books that invite them to think and to imagine, they need look no further than Johnson and Krauss.

"There, they will find a very special house, where holes are to dig, walls are a canvas and people are artists, drawing paths that take them anywhere they want to go."

First Published: September 4, 2012, 8:00 a.m.