It's a rare academic who turns his expertise into commercial success. But the man whose fertile and daunting imagination has spawned "eight or nine" (he isn't quite sure) worldwide productions of a megahit musical is somewhat bemused by the whole thing.

In a sense, it isn't even his. Gregory Maguire certainly wrote the novel "Wicked," his darkly revisionist 1995 version of "The Wizard of Oz." And his story is the heart of "Wicked," the 2003 musical by Stephen Schwartz (music, lyrics) and Winnie Holtzman (book) that on Wednesday will log its 2,000th performance on Broadway, the same day one of those tours sets up shop for five weeks at the Benedum Center on its second visit to Pittsburgh.

But book and musical are different beasts. Although Maguire admires the more sugary version of his very different material, and he certainly appreciates the substantial income it generates, he says it took four or five visits before he could relax and accept its upbeat ending.

And then history moved onward, as history does. In an op-ed piece he wrote for the Boston Globe a year ago, when "Wicked" made a return visit to Boston, Maguire explained how his creation has come to speak with prescience of developments in the American body politic. What initially seemed sugary on Broadway and what attracts a young audience with little interest in politics has turned out, over time, to be closer to the dark fantasy he originally wrote. It isn't even so fantastic.

If none of this matches your memory of "The Wizard of Oz," the book or the 1939 movie, well, Maguire's isn't that "Wizard of Oz." His genius was to create a back story for the so-called Wicked Witch of the West and make her his novel's moral and sympathetic center. That required a new villain -- the Wizard and, in a more complex way, Glinda the Good. This is how he summarized it for the Globe:

" 'Wicked' is a story about an awkward girl, one with nascent magical powers and a steely sense of righteousness, who comes up against a ditzy opportunist named Glinda and a megalomaniacal dictator calling himself the Wizard of Oz. I modeled the green-skinned witch, Elphaba, after my heroines ... the young Virginia Woolf, for her acerbity and intellect ... the young Laura Nyro, for her invention and energy, and ... the older Emily Dickinson, for her willingness to retire when the going gets unseemly."

Maguire's Oz, he says, is less L. Frank Baum's escapist fantasy than it is "Pinochet's Chile and Hitler's Deutschland, seasoned with a bit of Orwell's '1984.' The Wizard was more Idi Amin than Lord Voldemort."

It doesn't sound like the stuff of a family musical. As Maguire says, the musical's creators "crystallized" his story "into a pink-and-green music box."

But with the cooperation of the contested 2000 election, 9/11, Afghanistan, Iraq, Katrina, Darfur and our increasingly shrill national discourse (that's his list), his original novelistic insight is clearer than ever: that the "cost of the choices one has to make may bankrupt even the morally soundest." Maguire wrote "Wicked" as a tragedy he hoped would "evoke the sort of feeling of Shakespeare or Greek tragedy, that you can't sidestep fate."

If that sounds stern, Maguire himself sounds anything but. A resident of Concord, Mass., he was interviewed by phone last week while on vacation in Maine, after having spent half the summer in Europe. His tone is enthusiastic, full of bemused curiosity about the workings of the world.

He says he's been largely consumed in recent years with child-rearing -- he and his husband, painter Andy Newman, have three adopted children, ages 7, 8 and 10. But he's still writing and publishing at a steady rate, including "Son of a Witch," the second part of his Oz epic, with a third part, "A Lion Among Men," due out in October.

Maguire, 54, for a decade taught children's literature at Simmons College, but mainly he has written it -- some 20 novels over 30 years. "Wicked" was the first of his adult novels, and he has continued to reinterpret famous stories with "Confessions of an Ugly Step Sister" (based on "Cinderella"), "Lost" ("A Christmas Carol") and "Mirror, Mirror" ("Snow White"). He calls "What the Dickens," published last year, "my first serious book."

When there was initial interest in turning "Wicked" into a Broadway musical, he says he figured there was about a 1-in-1,000 chance of it coming to fruition. When composer Stephen Schwartz came to see him, he had already written the opening number, "Nobody Mourns the Wicked," which convinced Maguire it wasn't going to turn into some sort of "Saturday Night Live" parody. So he gave his permission and sat back to let it happen as an experience, if nothing else.

"I felt fairly liberated, because I realized that L. Frank Baum had not come out of the grave to scream at me," when he performed his own act of appropriation.

Then a year before the San Francisco premiere, there was a full reading for 100 people, and he found himself "impressed, even moved" -- until the surprise happy ending. But he realizes that a musical comedy is a different beast than an artful adult novel. And he feels the tragedy he wrote is still present in the death of the romance between Elphaba and Glinda. So "I forgive the slightly Disneyfied ending."

He's astonished at the popular response. He says the first night in San Francisco was explosive. Idina Menzel as Elphaba "could have been singing the phone book or in Sanskrit -- the hair on the back of my head stood up. I thought, 'this is going to work even if it's bad.' "

For more on Maguire, visit www.gregorymaguire.com.