Retiring at 41 is easy; the problem, as ""fussy man"" Rust Hills sees it, is living with a self no longer defined by a middle-class job title and getting used to hearing one's name mentioned in the past tense (Rust Hills was fiction editor of Esquire). Recalling his own slide into compulsive list making -- ending with the Comprehensive Day Plan which took an hour or so just to construct -- and his battle against general decrepitude (""If you really want to know what it's like to retire at 41, read Molloy""), Hills recommends likely time-filling pursuits: bill-paying and buying sporting equipment are good; free-lance writing is only for masochists. Of course the man who is ""retired"" at 41 is in a distinct class from otherwise non- or unemployed persons and destined to work out a new persona through trial and error, suffering, and imaginary dialogues with disapproving cleaning ladies. But Hill knows how to glean insights from other early retirees like Montaigne, the Prisoner of Zenda, and that lucky fellow Thoreau, for whom solitude was ""not so much isolation. . .as occupation."" And if his proposed Leisure Ethic won't solve all the problems of this ""utterly depraved age,"" it does give us something to ponder while schlepping through the 9-to-5 routine.