Like a lot of people a decade or so out of college, A.J. Jacobs wished he'd learned more while he was there -- or could remember a respectable chunk of what he did learn. Like almost no one, he decided the best remedy for his ''long, slow slide into dumbness'' would be to read the entire Encyclopedia Britannica, from a-ak (''Ancient East Asian music'') to Zywiec (a town in south-central Poland). After years of working at magazines like Entertainment Weekly and Esquire, Jacobs' brain was brimming with ''pop culture jetsam'' that he fully intended to replace with actual knowledge about history, science, and the deeds of great men and women. What he winds up with by the end of this amiable and funny memoir of the year he spent reading the world's greatest encyclopedia is really just a higher class of jetsam.
The Know-It-All: One Man's Humble Quest to Become the Smartest Person in the World is mostly a collection of odd facts and silly anecdotes, so breezy you half expect to see the words lift off the page and float around the room. Jacobs keeps it battened down by bringing in some family history and his frustrating efforts to conceive a child with his wife, Julie. It's just enough to prevent the book from melting away as quickly as your grasp of high school calculus.
Jacobs knows that reading the Britannica won't really make him the smartest person in the world, but he does hope to hold his own among a daunting assortment of brainy relatives. His attorney father (who tried the same stunt when A.J. was in high school) has published 24 law books and holds the world's record for most footnotes in a legal article (4,824), his aunt is a professor of German literature at Yale, and his 11-year-old cousin hands out citations for grammar violations at family gatherings. Worst of all is his insufferable brother-in-law, who needles Jacobs mercilessly for his ignorance of the Crimean War and the difference between fusion and fission, and who wallops him at Trivial Pursuit.
Britannica entries for ''industrial engineering'' and ''lector'' help Jacobs load the dishwasher more efficiently and improve his presentations at work, but most of the information he acquires just goes toward annoying his wife, who finally resorts to fining him every time he blurts out an ''irrelevant fact.'' Those include everything from ''The Eskimos and the Zulus are both adept at the art of ventriloquism'' to the skinny on French philosopher René Descartes' fetish for cross-eyed women. Wisdom proves harder to come by, although history does lead Jacobs to the sage advice that you should never trust a politician nicknamed ''Uncle'' or ''Papa.''
Occasionally Jacobs takes his newfound expertise out for a spin -- at a Mensa meeting, in front of a college debate club, and finally as a contestant on Who Wants to Be a Millionaire, with the results ranging from inconclusive to disastrous. Did the Britannica make Jacobs smarter? Hard to say. Whatever genius it took to turn the weighty task of reading the encyclopedia into such an entertaining frolic of a book, my bet is that Jacobs had it all along.