Norton Juster, an acclaimed architect and children's author, best known for his classic 1961 novel, The Phantom Tollbooth (illustrated by Jules Feiffer, passed away at the age of 91.

Juster's other classic works include 1963's The Dot and the Line: A Romance in Lower Mathematics and the 2005 picture book, The Hello, Goodbye Window, which won the illustrator of that book, Chris Raschka, the Caldecott Medal in 2006.

Juster was born in Brooklyn in 1929. His father, a Romanian immigrant, had become an architect through a correspondence course and both Juster and his brother became architects, as well. Juster graduated from the University of Pennsylvania in 1952, where he studied architecture. He then studied city planning at the University of Liverpool. Following his academic studies, he then enlisted into the Civil Engineer Corps of the United States Navy. Juster rose in the ranks of the Navy, but he was also reprimanded once for writing and illustrating a children's book while on duty.

While posted at the Brooklyn Naval Yard, Juster met artist Jules Feiffer for the first time and the two became lifelong friends. When Juster left the Navy, he began to work for an architectural firm in Manhattan while also teaching part-time. He and Feiffer shared a house and when Juster received a grant in 1958 to write a children's book about cities, his idea evolved into a fantasy adventure instead. He talked about the project with Feiffer and the artist became interested in it, as well, and they soon sold their new book idea to Random House, leading to the release of The Phantom Tollbooth in 1961, with Feiffer doing the illustrations for the fantasy adventure novel.

The book was an immediate sensation (the Ford Foundation, who had awarded Juster the grant for the book about cities, were fine with the fact that he had evolved his initial book idea into a whole other direction) and Juster followed it up with The Dot and the Line: A Romance in Lower Mathematics, which he illustrated himself. Famed animator Chuck Jones adapted The Dot and the Line into a short animated film that won the 1966 Academy Award for Best Animated Short Film. Jones then also adapted The Phantom Tollbooth into a feature length animated film in 1970. Despite his new success as a writer, Juster did not give up his main career as an architect.

He maintained his own architectural firm in Massachusetts called Juster Pope Associates and he taught architecture and environmental design at Hampshire College for over two decades. After he retired from architecture, Juster continued to write, with his 2005 picture book, The Hello, Goodbye Window, followed by a 2008 sequel, Sourpuss and Sweetie Pie.

Juster even reunited with Feiffer in 2010 for a new book, The Odious Ogre, nearly fifty years after their first hit collaboration.

Successful children's author and longtime friend of Juster, Mo Willems, shared a tribute to his former lunch partner, on Twitter.