CHARLES AT FIFTY

CHARLES AT FIFTY Anthony Holden (Random House, $24.95) Prince Charles, as represented here, is a real shlub, a guy who whines about everything. In other words, he's the same guy who has already been exhaustively chronicled in myriad other books, not to mention newspapers, magazines, and TV shows. In fact, the book reads like a compendium of clippings, with a decidedly pro-Diana slant (at one point, Holden compares Charles to King Lear before he saw the light). The explanation may be buried in the introduction: During Holden's first two bios of Charles, the future king cooperated, but sometime after No. 2, Charles got mad and shut Holden out. Spurned biographers don't just get mad; they get even. C-