By Sidney Poitier
304 pages. HarperCollins.
Some people aren't satisfied to be dashing, principled, talented, influential, and legendary; they have to keep giving of themselves. In Life Beyond Measure: Letters to My Great-Granddaughter (HarperCollins), actor Sidney Poitier unaffectedly muses on life's mysteries, as compelling as ever in his ninth decade. "Those who stop their questioning—" he informs his tiny relative, "at 75, 60, even at 30—cut short their explorations and end up with permanently unfinished lives."