In his paintings of a century ago, Georges Seurat demanded that the world look at art in a shocking new way. In "Sunday in the Park With George," their new show about Seurat, the songwriter Stephen Sondheim and the playwright-director James Lapine demand that an audience radically change its whole way of looking at the Broadway musical. Seurat, the authors remind us, never sold a painting; it's anyone's guess whether the public will be shocked or delighted by "Sunday in the Park." What I do know is that Mr. Sondheim and Mr. Lapine have created an audacious, haunting and, in its own intensely personal way, touching work. Even when it fails—as it does on occasion—"Sunday in the Park" is setting the stage for even more sustained theatrical innovations yet to come.

If anything, the show … owes more to the Off Broadway avant-garde than it does to...