Onstage, of course, we don't have hundreds of pages to let the ambitious tale breathe. We've got 2½ hours. So the sheer number of tragedies makes 'The Kite Runner' an especially tough story to adapt without turning it into a soap opera - an emotional shellacking. That treacherous trap, however, is shrewdly avoided on Broadway, where a moving stage adaptation of the book opened Thursday night, because of the actors' radiating warmth and the production's generosity of spirit. It's a straightforward, to-the-point play, but one that's easy to embrace and gripping as it unfurls.