Word on the literary street is that Jonathan Lethem could be the next Jonathan Franzen. Franzen had his success with "The Corrections," a sprawling literary novel about America. Lethem's new novel, "The Fortress of Solitude," takes an equally big slice out of the American pie. Officially, Lethem's publisher, Doubleday, won't go near such a comparison, although editor in chief Bill Thomas thinks Lethem's book will do well, "and I don't just mean sell well. I mean this book will be read by my son's grandchildren." The most Lethem himself will brag is to say that, until now, "I didn't have the chops or the maturity to do it right," meaning, plainly, that now he does. And he's right. This quasi-autobiographical epic about Brooklyn and black-white friendship isn't perfect, but it's got enough material to keep four or five smaller novels going. The big difference between Franzen and Lethem? Franzen looked down his nose at Oprah. Lethem thinks being a Pennie's Pick at Costco (that would be the head book buyer's endorsement) is dandy.