The long fall

A brand-new mystery series from one of the country's best-known, best-loved writers: a new character, a new city, a new era. A new Walter Mosley.His name is etched on the door of his Manhattan office: LEONID McGILL, PRIVATE INVESTIGATOR. It's a name that takes a little explaining, but he's used to it. "Daddy was a communist and great-great-Granddaddy was a slave master from Scotland. You know, the black man's family tree is mostly root. Whatever you see aboveground is only a hint at the real story."Ex-boxer, hard drinker, in a business that trades mostly in cash and favors: McGill's an…