Ultraluminous by Katherine Faw Farrar, Straus and Giroux, $25.00, 199 pages, ISBN 978-0-374-27966-0 This weeks MBR is one of those which are unclassifiable . . . it’s hard-boiled, cutting edge, semi-pornographic, unapologetic, compelling and utterly fascinating . . . but don’t say we didn’t warn ya. Ultraluminous, by Katherine Faw, comes four years after her astonishing and powerful debut, Young God. If Ms. Faw took the literary world by