Bred in Chicago's suburbs, Tom Groneberg got hooked on horses during a summer stint at a dude ranch, and moved to Montana to indulge his inner John Wayne. In The Secret Life of Cowboys, a series of eloquent vignettes, he describes the sounds and smells of the ranching routine (the stickiness of a calf birth, the persistent crying of a branding session) in a sharp, immediate tone that will lure even the most aloof city slicker: ''The whole world looks like a Copenhagen ad or a Marlboro commercial.'' And the whole world offers a primal and romantic thrill until it comes time to euthanize a sick animal or add up the bills. Groneberg brings poignant, sober honesty to a range where sentimentality and fear have no home.

