This week's ranks welcome Joe Biden, whose preciously titled new book Promises to Keep debuts in the No. 2 slot. The veteran politician and occasional misstepper has persisted as a formidable contender in the Democratic nomination race. But it may be the strategic publishing of a new hardback that keeps him in step with the well-moneyed camps of Barack and Hillary—or at least help secure his name on the shortlist for a secretary of state nod in '08.