James Stewart’s calculus text books made him very rich. He spent his fortune on Integral House, an award-winning architectural marvel inspired by calculus, which is now on sale after he died last year

This article is more than 4 years old

This article is more than 4 years old

James Stewart was an unlikely literary sensation.

The Canadian mathematician made a multimillion-dollar fortune by writing calculus textbooks for universities and high schools. Last year alone he sold 500,000 books, accounting for about $26.6m (£17.5m) in sales, according to his estate.

Stewart was also an unlikely architectural trailblazer. He devoted many years of his life, and much of his income, to building his dream home in an upmarket Toronto neighbourhood. Integral House – named after the “integral”, a concept in calculus – is a shrine to calculus, the mathematics of flowing change.

Facebook Twitter Pinterest With apologies to Plato, but how about a plaque that says ‘Let no one untrained in calculus enter here’? Photograph: Sotheby's International Realty

Stewart died last December, aged 73, and Integral House is now for sale at £11.4m .



“The house is a piece of art,” said Paul Maranger, of Sotheby’s International Realty. “When buyers go into the house the first reaction is a sense of awe.”

Facebook Twitter Pinterest Balcony view: the house doubles as a concert venue. Photograph: Sotheby's International Realty

Stewart, whose other passion apart from maths was music, had two requirements he wanted the architects to meet: he wanted a house that was based on curves - which would require calculus in the design - and he wanted it to include a concert space.

After meeting with many top architects, he commissioned the Canadians Brigitte Shim and Howard Sutcliffe to come up with a design. Building work began in 2003 and finished in 2009. The house, at 194 Roxborough Drive, Rosedale, Toronto, cost more than £15m.

“I think it’s one of the most important private houses built in North America in a long time,” Glenn D Lowry, director of New York’s Museum of Modern Art, told the Wall Street Journal. “The curved walls make it almost impossible to relate it to spaces that you know. It’s one of the most remarkable houses I’ve ever been in.”

Facebook Twitter Pinterest Ahead of the curve: beautiful bench and shelf combo. Photograph: Sotheby's International Realty

“I think the person who buys this house will be someone who likes to entertain,” said Maranger. “Not many houses were built as a concert hall. It was designed for a traffic flow of a couple of hundred people.”

Facebook Twitter Pinterest Lounge lover. Photograph: Sotheby's International Realty

Stewart studied at Stanford and Toronto universities, and was a postdoctoral fellow at the University of London researching harmonic and functional analysis. By the late 1970s he was back in Canada, at McMaster University, Ontario, when one day he was approached by two of his students who suggested he write a calculus textbook, since his lecture notes were better than the book they were using.



He started writing. Together with his teaching and research he worked for 13 hours a day until his first book was finished seven years later. His dedication paid off - it was the first of about 30 books that catapulted him into the bestsellers lists.

“He was the rock star of the calculus world. His books were no 1 in China. He was for years no 1 in the US,” says Maranger.

Facebook Twitter Pinterest Embedding theorems. Photograph: Sotheby's International Realty

Don’t be surprised if you have never heard of him, though. Stewart’s books are generally only known by students studying maths, or maths-based subjects. And some of his books cost well over £100.

Facebook Twitter Pinterest Study with a view. Photograph: Sotheby's International Realty

Stewart was diagnosed with a rare blood cancer in 2013. He carried on writing calculus text books until he died in December last year.

Facebook Twitter Pinterest Shelfie. Photograph: Sotheby's International Realty

Maranger said Stewart was a passionate about his work: “The book shelf had three distinct areas: far left was the books he wrote, centre was the books he collaborated on and the right was the competition.”

Facebook Twitter Pinterest Another shelfie. Photograph: Sotheby's International Realty

The house was a lifetime project and everything in it was custom built. The floors were laser cut in France.

Facebook Twitter Pinterest Garden. Photograph: Sotheby's International Realty

From the windows you cannot see any other house.

Facebook Twitter Pinterest Maths table. Photograph: Sotheby's International Realty

Maranger added: “He thought electrical outlets were ugly so you can’t see any. If standing in the middle of the room you cannot see any plugs.”

Facebook Twitter Pinterest Calculus of infinitesimals, and infinity pools. Photograph: Sotheby's International Realty

James Stewart was active in LGBT campaigning and frequently gave his house over for fundraisers. Both Philip Glass and Steve Reich have played there. Before he died he said he hoped his house would continue to be used for these sort of events.

Facebook Twitter Pinterest James Stewart...and an integral symbol! Photograph: Don Smith

It is hoped a buyer is found who has a love of music, sharing - and mathematics.

My latest book Snowflake Seashell Star: Colouring Adventures in Numberland is a maths colouring book, and it contains some images from calculus, like this one here. I hope James Stewart would have approved!