There was some excitement recently at the offices of Transworld, publisher of the British thriller writer Lee Child, who has so successful conquered America with his Jack Reacher adventures. Child usually produces only one novel featuring his tough ex-army action hero each year, but the latest book, 61 Hours, will be followed up with a speedily issued second new Reacher-related novel this autumn. 61 Hours -- admirers will, of course, have to have both. Sales of such Child novels as Gone Tomorrow have exceed 74,000 copies