In 2011, "The Annotated Phantom Tollbooth" was published, which includes sketches and copies of Juster's handwritten drafts and word lists, Feiffer's early drawings, and an introduction and annotations by Leonard S. Marcus. A fiftieth anniversary edition was also published, with appreciations by Maurice Sendak, Michael Chabon and Philip Pullman. More than three million copies have been sold of the original book in the U.S. alone. It has been adapted into a small-scale opera with music by Arnold Black, and a book by Juster and Sheldon Harnick, produced by Opera Delaware in 1995. It was then revamped into a musical that had its debut to strong reviews at the Kennedy Center in Washington, D.C., and then made a national tour.