While others have drained the smoggy mystique of the garment center for its more robustly available elements--from schmooz to showroom sex--Horowitz illuminates the way of the merchantman with a lasar probe and kultur recognitions. Sammy runs because he runs, in a race where the circular track itself is goad, good and goal. And this is the fulfillment of the running man: ""He acted like a happy professional doing the best job he knows how. . . he felt a little bit of peace, a little bit of joy. The surface was as smooth as whipped cream; the inside doors were locked up for the night."" On his way up, young designer Philip Hanssler, finding his way from Teaneck, New Jersey, to a top signature in women's clothing, eventually learns how to close doors, firmly and forever. This is also the story of the Jewish fathers who led their companies' forces on the Avenue--A. J. Fleiss, who coasted disastrously on the good old days of success; handsome, bitchy Carl Kalb, with whom Philip had drifted into an affair; the Greenstalks, who were moving in and with the competent manipulations of Marvin Bernstein, spawned new enterprises like killer whales. Then there are those tentatively reaching out to love Philip--Howie, who wanted more to life than the means: Wilma. whom Philip marries (""why not?""); and Marvin, with whom he contemplates an intimacy with no mystery, no threat. For as Philip had confessed to Howie--""I'm an end product, a result, not a goddam cause,"" and love is an adjustment, an arrangement, not a beginning. . . . In probably the best novel that will ever be written about the garment center. Horowitz, in its own words, ""shows classmanship.