HOME Is where the heart is. Home is hearth and family. Or, if you live in Toronto, home is a mortgage the size of a millstone, and its value as a piece of real estate the only topic of conversation. Not so for Witold Rybczynski, for whom home is still an idea and an ideal.

When Witold Rybczynski (the name is pronounced Veetold Rib?chin?ski, with the emphasis on the vee and the chin) wrote Home: A Short History of an Idea in 1986, he took critics by surprise and readers by storm. Who was this McGill University professor of architecture, this Canadian John McPhee who made his subject so compelling? Well, he was an architect who had become a writer. Home, testament to that writer's range and curiosity, was about comfort and our pursuit through time of that notion. It ended with a challenge: that we resist the advice of experts (including architects) and seek out a. definition of domestic comfort that is our own.

In The Most Beautiful House in the World he returns to that theme. The most beautiful house in the World, he argues, is the one you build yourself. The book is a journey, and begins as all journeys must, with a dream. Rybczynski's dream was of a boat, and further, of building that boat in a workshop somewhere. But where? Economic necessity forced the author and his wife, Shirley Hallam, to consider land south of Montreal. In the book, choosing the site leads to the concept of feng?shui a Chinese "cosmic surveying tool." Feng?skui is a more ancient and spiritual version of the real estate agent's dictum "location location location." In the end Rybczynski relied on instinct. And why not? The corner of an abandoned apple orchard was now his.

I said the book was a journey, and journeys are full of, surprises. Rybczynski came to love the meadow where his workshop would be, and he wondered about adding on a house. And so began a process of evolution. Architecture, "that seeming blend of technology and art" as the author puts it, inspired over a five?year period the contents of two notebooks as the edifice was repeatedly recast: "Building on paper had been an effortless process. A sweep of the eraser was enough to abolish a wall; two darts of the pencil and it reappeared elsewhere." Now a ship's cabin, now "two little buildings," now sore thumb on the land scape, now barn?shaped home that blended nicely into the rural Quebec context. The conception and physical construction of what the author came to call 'Me Boathouse were never simple acts. False starts and dead ends. marked a path that at times seemed glorious.

He writes of the energetic driving of nails into soft pine and the slower and more exacting operations of measuring and cutting. When we stopped, as did often, the tapping of hammer on nail head and the scraping of saw through wood were replaced by the meadow sounds of birdsong and the chirping of crickets.

But this re?enactment of an ancient ritual ? building one's shelter ? and the resulting satisfaction, were tempered by other, less romantic realities:

Lacking experience, I had made demoralizing mistakes and had to redo work, sometimes several times. Shirley and I grew cranky: we argued. Instead of escaping for weekends to the country, we began to look forward to returning to the city on Sunday night. We took increasingly frequent "vacations" from what came to feel like a neverending Sisyphean penance.

But the marriage endured, as did Rybczynski's romantic ideals. Quoting Gaston Bachelard, Rybczynski writes that the chief benefit of the house is "to shelter daydreaming." Some, perhaps crankier, would counter that a house is for constantly fixing ,and they would do well to steer clear of this book. Which is, after all, about ideas. How is design like play? What does a cowshed have in common with a cathedral? When does a building become a piece of architecture? (There is, too, much information: How many children around the world play with Lego, the plastic construction blocks? Answer: 68 million children in 125 countries. "We have all been," concludes Rybczynski, "little architects.")

I admire Rybczynski's ability to ferret out eccentric detail. He takes us to the unique homes of prominent writers, such as George Bernard Shaw, Whose eight?foot square writing shed (he called it The Shelter) was built on a central steel pipe, allowing the whole affair to be revolved to meet the warming sun. Freighted with books, The Shelter never slipped anchor. Rybczynski's own bit of solar worship in The Boathouse was a wall of recycled glass ? "a bacchanalian rose window" that at sunset "blazed with the amber and emerald colors of spent wine and liquor bottles."

Home was a hard act to follow. Its sequel, perhaps unavoidably, has the feel of a sequel. The writer never quite doffs his professorial robes, never leaps free of the podium. Less of a history lesson than Home, less revealing of the writer's character than you might expect, The Most Beautiful House in the World occupies a middle ground between erudition and personal story. It's an excuse to contemplate all that architecture embraces: "pattern language," the critical question of context, and the curious irony of architectural giants who have always worked in miniature.