Barnes &Noble's board of directors approved a "poison pill" provision earlier this month designed to prevent the bookstore chain from being acquired in a hostile takeover. Under the plan, B&N shareholders of record July 21 would receive the right to purchase a new class of preferred stock if an outside group acquired 15% of the company or announced a tender offer that would result in a third party controlling at least 15% of B&N. B&N said the shareholder rights plan "is not being done in response to any known effort to acquire the company, but is intended to protect the long-term value of the company for its shareholders in the event of any unsolicited attempt to acquire the company."