Advance publicity hails this ""story'' (not labeled a novel) by the popular writer as appealing to ``readers of all ages,'' although its genesis was in a story King told to his children. King's legion of fans are likely to find that a restrained maturity marks the differences between this stylish, successful effort at fantasy (illustrated by 21 half-tones) and his earlier, sometimes overwrought writings. Eyes details the crusade of Peter and Thomas, two princely brothers, to destroy the 400-year-old Flagg, the evil magician who threatens to control the kingdom of Delain after the death of their father, King Roland, who remained unwed until he was past 50. Flagg has imprisoned Peter, the heir apparent, on suspicion of murdering the king (actually it was Flagg who did it) and installed the profligate second son, an easier mark, on the throne. Surprisingly, Eyes is a gentle story, despite violence, gore and his standard vulgarity, because King has ingeniously interposed himself between reader and narrative as if he were telling the tale aloud, with a soothing cadence practically audible in the evocative prose. This heartwarming chronicle of brotherly love may be enjoyed by young adults and their parents. 1,000,000 first printing; $300,000 ad/promo; BOMC selection. (February 2)