Craig Ferguson isn’t kidding. That’s what struck me as I turned the pages of the Scottish late-night comedian’s memoir, “American on Purpose: The Improbable Adventures of an Unlikely Patriot.” Almost every time Ferguson has a chance to go for a cheap, easy laugh — the mother’s milk of late-night comedy — he runs in the opposite direction. Take the opening scene in which he meets George W. Bush at a reception before the 2008 White House Correspondents’ Association dinner, where Ferguson, a newly minted American citizen, is to be the entertainment. He recognizes that making fun of Bush near the end of his catastrophic presidency would be like shooting fish in a barrel, so what does he do instead? He bonds with Bush as a fellow recovering alcoholic, clinking glasses of sparkling water with him as the president makes an earnest toast to America. I repeat: this is the opening scene of a book by a comedian. That’s what we in the comedy business call courage, and it pretty much sets the tone for the rest of this memoir, in which Ferguson admirably avoids wisecracks and instead goes for something like wisdom.

The fact that Ferguson has the Scottish version of chutzpah shouldn’t come as a surprise to regular viewers of his TV program, “The Late Late Show,” on CBS. Since his debut as host in 2005, he has evolved into something of an anti-Leno, trading the rapid-fire delivery of canned topical jokes cooked up in a writers’ room for something more idiosyncratic and risky: a loopy, seemingly ad-libbed monologue in which he talks with, not at, the audience. (I say “seemingly” because Ferguson, of course, has a roomful of writers and is working from bullet points, but his performance skills are such that he makes his monologues sound like they’re something daft that just occurred to him.) There’s no one else like him on television, and he’s achieved something unusual in late night: a sense of intimacy with his audience. In “American on Purpose” he establishes a similar bond with the reader. Like Steve Martin in his similarly engaging memoir, “Born Standing Up,” Ferguson tells the life story of a comedian without letting jokes get in the way.

Born in 1962, he had the kind of grim childhood that seemed destined to result in a career in comedy. Chubby and bullied, he grew up in a city planner’s nightmare of a town called Cumbernauld, 15 miles outside Glasgow. (Ferguson notes that Cumbernauld was recently rated the ­second-worst town in the United Kingdom, an appraisal he finds unjustifiably flattering.) During an obligatory punk phase in the early ’80s in which he played drums for a band called the Dreamboys, he was fortunate to have as a band-mate the actor Peter Capaldi, who inspired him to try comedy. “Peter was the first person who told me that being funny was a gift and, when done well, was an art form,” he writes. “Up until this point, I had learned that being funny, particularly in school, was stupid and could get you physically injured.”

fter a first shot at comedy in which he was so visibly nervous that the audience started chanting “Iz knees are knockin!” he went back to the drawing board, inventing a character to play at a gong show in Glasgow. “I decided I would do a parody of all the über-patriotic native folk singers who seemed to infect every public performance in Scotland and appeared on local television every New Year in the annual orgy of maudlin, folksy sentimentality that the Scots call Hogmanay.” The character, Bing Hitler, eventually became a smash at the 1986 Edinburgh Festival Fringe, and Ferguson was on his way.