Becca Reinhart is a spitfire investment-firm partner from Brooklyn. She lives on espresso and the occasional bagel. (Yeah, she's Jewish.) Edward Kirkland is a racquetball-playing heir to a diamond fortune from Manhattan. He describes bagels as donuts, only ''harder, like [they're] stale.'' (Yep, he's a WASP.) This unsubtle opposites-attract tale has a Little Orphan Annie bonus: precocious, suddenly parentless 4-year-old Emily Stearns, who brings these singletons together. Brown, whose frothy debut novel, Legally Blonde, spawned the 2001 movie, is no master storyteller (you see the cheesy finale coming by about page 15), and her eagerness to capture the players' disparate inner voices creates an uneven tone. Like Kirkland's bagel, it's all kind of stale.