PICTURE Norm Abram of public television's "This Old House" hosting "Saturday Night Live." Or, better, humorist David Barry writing in the style of master explainer John McPhee. David Owen's "The Walls Around Us" is nearly as earnest as plaid-shirted Norm and occasionally as funny as Barry.Owen probably can't help it: No one could last long in an old (1790) country home with uncertain plumbing if one didn't have a sense of humor and a willingness to roll up one's sleeves. Having been an editor on the Harvard Lampoon and having had an affection for construction sites as a young lad must have helped, too. This is not a do-it-yourself guide written by a super-handyman, though it has lots of explanations and practical advice on such things as paint (oil vs. latex), septic systems ("No man is a hero in the eyes of his septic-tank pumper"), ice dams on your roof (don't bother with heating wires or metal sheathing - you need a better-ventilated attic), and how to talk the lingo of the guys down at the lumberyard. Anyone being shaped into a carpenter, plumber, painter, or all three by the exigencies of home ownership will experience flashes of self-recognition reading Owen's odyssey from novice to competent amateur-in-progress. "I began timidly at first, nailing down a loose board here, painstakingly ruining some old molding there. Each completed task, no matter how amateurishly executed, inflamed my appetite for harder and scarier projects.... What would I think of next? That is what my wife wanted to know." Owen recounts some significant successes - ceilings restored, a home office built, a new kitchen counter installed. Late in the book, however, he also owns up to having an upstairs bathroom with rotting wood trim, mildew on the ceiling, and long strips of duct tape ("a phenomenally versatile and durable material") laid clapboard-style over loose tiles. "Setting foot in this room would fill me with shame," he insists, "if my wife and I were not planning to transform it soon into two entirely new ... bathr ooms, one for us and one for our kids." ("Soon" is surely the slipperiest of handyperson terms.) This is not a history, either, though I found Owen's wry chronologies - of house paint and plasterwork, kitchen counters and plywood, among many others - to be some of the most useful and entertaining parts of the book. The forestry pavilion at the 1905 World's Fair in Portland, Ore., for example, was made with "three-ply veneer work the first plywood. The animal glue used to stick together the thin sheets of softwood smelled so bad that "the men frequently had to seek the comfort of outdoors," he quotes one source as saying. Thomas Jefferson spent 57 years happily working on Monticello, Owen notes. Thirty years after the building was begun, there was still no entrance hall floor: Guests had to step gingerly along boards laid over joists. Some passages are textbookish; in others, the humor is strained: It's hard to explain electricity in a humorous fashion, and I don't quite believe that buying lumber involved such trepidation. But Owen is at work on a noble structure, here, and can be forgiven his use of a few dull bricks and a little (perhaps) exaggeration. He's building a sturdy framework of house knowledge, distilled of book knowledge, observation, talks with (even lessons from) experts, and firsthand experience. In his cajoling way, Owen is empowering the home owner: You can do it, he says, and this is the real value of the book. There's even an index, chapter notes, and an annotated resource guide in the back. "Before I began to develop a sense of how my house works," Owen writes, "the things that went wrong with it seemed cruelly whimsical. Now I realize that every effect has a cause and that the causes can be discovered and understood.... I no longer feel as though I'm being held hostage by the box in which I live."