Robert Haft, 24, is launching a string of cutrate bookstores in the Washington area and hoping success runs in the family. His father is the founder of Dart drug stores which is bankrolling Haft's entry into the close world of bookselling, a venture that has other book stores watching warily.

"I think it is a come-on to sell remainders," scoffs the manager of Book Annex in Georgtown, referring to the marketing angle that sets Haft's Crown Books apart from other stores: a thirty-five per cent discount on hardback bestsellers.

"There's no secret to it," Haft says. "We're working on a very thin margin."

Crown's first outlet on Rockville Pike does indeed offer a large selection of remainders - books bought from publishers' overstocks - and a customer must pass by them to find the bestsellers, stocked in the rear of the store. (Not for nothing did young Haft earn a master's in design and, later, business at Harvard.)

Haft, a bachelor who makes his home in Georgetown, is planning outlets in the McLean-Vienna and Wheaton-Silver Spring areas. And because Dart is a publicly held company, Crown will have to report regularly to the Securities and Exchange Commission. Which means competitors who think Haft is losing money just to undersell them can keep an eye on their new competition's balance sheet.