Over the course of a conversation, Clayton Christensen — by turns engaged and engaging, expansive and thoughtful — will likely stumble over a word or two. On this particular occasion, it’s “grocery store,” the kind of small business his family owned and where Christensen fondly recalls weekends spent working with his dad.

He pauses to explain as he searches his brain for the term. “You see, I had a stroke and lost the ability to speak,” he says, as plainly as if he were excusing a sneeze.

Christensen, a Harvard Business School (HBS) professor and one of the top theorists of his time, has built a storied career by, as he puts it, telling business leaders not what to think, but how to think about running their companies. In the two years since his stroke, he’s tackled two other equally ambitious tasks: relearning how to speak, and teaching the rest of us how to think about living our best lives.

The result is a deeply personal book that puts years of Christensen’s observations on human behavior to paper, a process he calls “one of the most worthwhile endeavors of my life.”

“How Will You Measure Your Life?” — co-written with his former student James Allworth, M.B.A. ’10, and former Harvard Business Review editor Karen Dillon — was a labor of love for Christensen, author of the seminal business text “The Innovator’s Dilemma.”

Far from offering self-help or ways-to-succeed platitudes, the book takes on life’s big questions — how to balance work and home life, how to maintain a marriage and raise children, how to adhere to ethical and moral standards — using the rigorous framework of the business models Christensen has developed over two decades.

“At a fundamental level, good principles based on theory are relevant wherever you look,” he says. And just as a company has to not only measure profits and losses, but also determine whether its measures for promoting long-term success are the right ones, people need to figure out what happiness looks like to put it in reach.

“How we measure things determines what we do and what we don’t do,” says Christensen, Kim B. Clark Professor of Business Administration. We may say we value time spent with our families, for example, but if we measure our success day-to-day by how much money we’re making or how quickly we’re being promoted at work, then we may not find the happy family lives we envision for ourselves.

On its face, the idea may seem crass: To live a good, fulfilling life — one rich with meaningful relationships, rewarding work, and ethical behavior — simply think as the best CEOs do. But, as Christensen and his co-authors argue, applying sound theory to everyday decisions can help keep us on track.

Here he invokes one of the time-tested examples of disruption, the theory that made his name: the American auto industry, which was caught off guard years ago by the creeping success of Toyota and other cheaper imports. “Never did the management of General Motors and Ford get the board and the executives together and say, ‘Guys, let’s develop a plan to drive this company into bankruptcy,’” Christensen says. “They didn’t ever intend to ruin their company. But all of those well-meaning individual decisions that made sense, it sums up to what you don’t want to do.”

Just like the auto manufacturers’ strategies, our lives don’t veer off track at any particularly dramatic moment, he says — “and that’s the problem.”

“Almost always, when your life falls off the rails, it wasn’t an event,” he says. “It was a process, where piece by piece, what you did seemed to be innocuous or good. Most things that turn out to be bad choices, at the time we made them, seemed to be very rational. You just can’t allow yourself to get victimized by marginal-cost thinking.”

Christensen is no stranger to seeing smart, well-meaning people do just that. In his days as an HBS student and as a Rhodes scholar, he says, he met countless bright young people who have since drifted down the path toward business scandals, divorce, even prison. (The starkest example, perhaps, was that of his old HBS classmate, former Enron CEO Jeffrey Skilling.)

For Christensen, a devout Mormon and dedicated father, temptation to stray from his principles comes in the form of work, which constantly vies for his attention. “Because my work is so interesting, it could easily consume 18 hours a day, seven days a week,” he says. Years ago, he made an agreement with his wife and the mother of their five children, the youngest of whom is now a junior in college: “I will never work on Saturday or Sunday, and I’m always out of here by 6 p.m.”  (It helps, he admits, that he’s usually at work by 6:30 a.m.)

To hear Christensen’s energetic approach to his life — to hear him speak of helping others, of his faith, of tackling problems in business, health care, and education — it’s hard to imagine he was facing its end less than three years ago. In late 2009, he was diagnosed with an often fatal form of lymphoma.

His cancer diagnosis lent new urgency to the end-of-the-year talk he had been giving his M.B.A. students for two decades. In “Building and Sustaining a Successful Enterprise,” typically on the last day of class, he would challenge his students to apply the theories of the course to their own lives.

“At a certain point we thought, ‘We’ve been using these theories to examine companies; let’s just stick it on the mirror and use it on ourselves,’” says Christensen. “My students always came back with much deeper insight than I had ever come up with.”

Allworth, the book’s co-author, took the course in spring 2010, in what many thought might be Christensen’s last semester teaching it.

“If anything, I think it made him more determined to get through to us,” recalls Allworth, who put his postgraduation plans on hold to help Christensen research and write the book.

That same spring, HBS invited Christensen to speak to graduating M.B.A.s at their Class Day ceremonies in Burden Hall, an event that caught the attention of Dillon, who would become the final member of the book-writing trio. Then the editor of Harvard Business Review (HBR), she decided to interview Christensen about his ideas on how to live a good life to adapt into an HBR essay.

“I walked into Morgan Hall thinking only about that article, about getting it done,” Dillon says of her initial interview in the professor’s office. “I walked out an hour and a half later thinking about myself and my own life. … There were questions rattling around in my head, and I didn’t like the answers to them.”

She was struck by Christensen’s engaging conversational style — “a cross between my childhood minister and Jimmy Stewart,” she jokes. “He has this lovely, good-moral-fiber, salt-of-the-earth quality. You want to be sitting on the edge of our chair with your hands on your knees.”

But she was also inspired by what she calls the “intellectual challenge” of his words. In the following months, she quit her job, took up part-time freelance work, and plotted a move to London with her British husband and two children to reset her priorities. (Meanwhile, Christensen’s HBR essay went viral — it’s still the most-read article in Harvard Business Review’s history, according to Dillon.) Eventually, Christensen came calling again, and she joined work on the book, aided by “Dropbox, Skype, and Google Docs,” she says with a laugh.

The writing proceeded haltingly. Just a few months after his cancer went into remission, Christensen suffered the massive stroke that affected his ability to speak. The three co-authors had already agreed the book should be written in Christensen’s voice, and the process of putting his longtime thoughts to paper became even more challenging.

The writing also stimulated a fair amount of debate among Christensen, a lifelong Mormon; Allworth, an atheist; and Dillon, a “classic New England Protestant” who fell soundly in the middle.

“I didn’t want to inadvertently write a book that applies only to religious people like myself,” Christensen says. “I wanted it to be fundamental enough that people across the spectrum could see real value in it.”

The result is more a crash course in business theory and common-sense thinking than in moral philosophy.

“One of the things that was important to us was making sure the theory was really accessible,” Allworth says, “almost like taking a minicourse of Clay’s class.”

Since its publication this spring, the book has held a steady spot on a number of best-seller lists, including that of The New York Times. Christensen plans to continue his end-of-the-year classroom lecture, though he acknowledges his students now have access to a 200-page primer.

“I’m worried, actually — now they can just read the book,” he says with a laugh. “I’ll have to come up with something that still excites them to think deeply about these problems.”

Yard full of fun