“Readers are not supposed to notice the structure,” advises acclaimed New Yorker staff writer John McPhee in Draft No. 4 (Farrar Straus and Giroux, $25), his collection of essays on craft. “It is meant to be about as visible as someone’s bones.” Counter-intuitively, perhaps, McPhee employs a variety of elaborate diagrams, charts, and in one case a doodle involving a turtle, a weasel, and a muskrat, to take a story from conception to a polished magazine piece that might run to as many as 80,000 words. So it comes as something of a relief to learn that this author of more than thirty books doesn’t always know what he is doing when he embarks on a new project. “Sometimes in a nervous frenzy I just fling words as if I were flinging mud at a wall. Blurt out, heave out, babble out something —-anything —-as a first draft.” Or that he once found himself up against a deadline, sprawled on the floor “near tears in a catatonic swivit,” with but one sentence written. This slim, entertaining volume also offers reportage on reporting itself, including McPhee’s struggle to convince a reluctant Jackie Gleason to cooperate for a Time magazine profile in 1961, as well as “two highly germane anecdotes” involving food and the legendary New Yorker editor William Shawn. McPhee is surprisingly funny in a wonky, droll, practical, grammarian sort of way. Is the plural of attorney general “attorneys general” or “attorney generals?” And what do you do with a bunch of attorney(s) general(s) and the ensuing apostrophe(s) when they possess objects (in the plural), such as, for example, cars? Mr. McPhee will make you care about the answer, regardless of whether it will ever figure in any sentence you may one day write.