This big, bold, beautiful and thoroughly impressive show fills the huge (by Broadway standards) Gershwin Theatre. That is no mean feat - many a musical that has played this house has seemed to be swallowed up in its cavernous space. But set designer Eugene Lee has packed the stage with a fantastical set of twirling gears, cables and platforms, Director Joe Mantello has assembled a fabulous cast including Kristin Chenoweth and Idina Menzel, and Winnie Holzman has found a way to tell most of the story from Gregory Maguire’s fantasy novel of what transpired in Oz before Dorothy was blown there by the cyclone.

Storyline: Glinda, who would ever be known as “The Good Witch” as a result of the movie “The Wizard of Oz,” and Elphaba, who would be known as “The Wicked Witch of the West” were, in fact, college roommates in their youth. How that came to be, why Elphaba was green, what the Wizard’s reign was like and how other characters from that famous story/movie came to be a tin man, a lion and a scarecrow, is the basis for this musical extravaganza staged as only Broadway could present it.

Just who is the top billed star is hard to say, for Kristin Chenoweth’s name is farthest to the left while Idina Menzel’s is higher up. But it is Menzel that has the more intriguing role and she makes the most of it. The show starts strong with Chenoweth’s opening number (“No One Mourns the Wicked”) but seems to settle into a too-lengthy period of exposition to explain the complicated plot line to the audience. It comes back to life with Menzel’s thrilling rendition of “The Wizard and I.” With that number she seems to establish herself and her role as the real driver of the evening’s delights.

Names listed in the program below the title include some very well known people doing some very good work. Joel Grey, as the Wizard, is “Wonderful” in the song of that name. Carole Shelley is a delight as the evil Madame Morrible. William Youmans is touching as a goat loosing his career as a college professor and his ability to speak as a result of an evil plot. And Norbert Leo Butz is, as he most often is, impressively distinct and convincing in his vocals, especially “As Long As You’re Mine.”

This score, by Stephen Schwartz sounds very much like something we would expect from the composer/lyricist of Godspell and Pippin who collaborated on songs for “Pocahontas” and “The Hunchback of Notre Dame.” They are folk-rock flavored pieces with a tendency to lushness in the melody, pop influence in the rhythms and spirituality in the lyrics. All of this works well for this show. Once upon a time it was also necessary to assess whether any “hits” would emerge from a show, but it has been a long time since Broadway shows generated hit songs - now it seems the other way around. These numbers do have the virtue of making effective scenes for the show and provide the cast with opportunities to shine - opportunities never wasted by this particularly splendid cast.