In the wake of James Stewart’s death on Dec. 3 at age 73, the Toronto mathematics professor is remembered as a philanthropist, a skilled violinist and former concertmaster, and as the owner of the five-storey architectural marvel known as Integral House, in which he lived and hosted concerts by the likes of Philip Glass and Steve Reich. He was also an unassuming titan in the educational publishing industry, as the best-selling author of calculus textbooks, a category he dominated for nearly 30 years.

“He’s the most published mathematician in history,” says filmmaker Joe Clement, who is directing a documentary about Stewart’s life. “And nobody knows anything about him. It’s crazy. Great subject for a documentary, though.”

In 1987 when Stewart’s Calculus entered the market, there were four major university-level calculus textbooks, which sold in nearly equal shares. Today, Calculus, which recently reached its 8th edition, is used globally by about 70 per cent of students of mathematics, science, and engineering. At nearly $150 a pop, Stewart may have been the richest author Canada has ever seen. At the very least, his earnings went a far way toward paying for the $32-million Integral House, for which architects Brigitte Shim and Howard Sutcliffe received the 2012 Governor General’s Award for Architecture.

Stewart, a professor of mathematics emeritus at McMaster University, began publishing his books with U.S. company Brooks/Cole (later acquired by his current publisher, Boston-based Cengage Learning). In a 2009 interview with the Mathematical Association of America, he said, “I’ve set out to do two major things in my life, but I didn’t think of them as major at the time. I just thought, ‘My two students suggested that I write a calculus book; I think I’ll write a calculus book.’ Look what happened. And then I thought, ‘It would be nice to build a brand-new house.’ I naively went about interviewing architects, and look what happened.”

His former editor, Gary Ostedt, says, “It’s difficult to talk about a guy like him, because he’s so out of the mainstream, in terms of his abilities. He was really a phenomenon in mathematics publishing. I don’t think we’ll ever see one like that again, I really don’t. He’s the only one that I’ve ever seen completely dominate a market like he has.”

At Cengage, where they refer to “the Stewart franchise,” his singularity is something of a double-edged sword. Despite the company having a succession plan in place, Ostedt says, “It’s hard to say if they’re going to sell as well as they have now that Jim is not involved.”

Balraj Kalsi, Cengage’s vice-president of math, science and qualitative business products, says the brand will “continue to be a very long-lived franchise. Before he passed, we discussed this with Jim, and that was one of the most important things to him – that the franchise live on.”

While the book’s new principal author has yet to be named publicly, there is time: Cengage has until 2018 to put out its next edition with updated calculus problems and, if necessary, revised sections.

“There’s a long precedent in the [educational publishing] industry where we’ve had authors pass away and we look to treat the succession plan with the most respect and responsibility for what’s been going before,” says Kalsi. “The challenge for all books is to keep the quality of authorship high. There’s the quality of the actual writing, the quality of the accuracy, and then the quality in terms of new ideas and innovation that are brought to the table. In this particular case, the challenge is just that Jim was very good at all three of those.”