As expected, “activist” investor Ron Burkle revealed yesterday that he has taken the next logical step in his battle with Barnes & Noble, suing the company’s board in a Delaware Court. In his SEC filing, he disclosed additional purchases of BN shares in recent days as well, now controlling a 19.62 percent stake–just below the 20 percent limit of the company’s poison pill. In the lawsuit Burkle rails against a “self-dealing scheme designed to entrench the Riggio family in their control of Barnes & Noble and prevent an effective proxy contest from being mounted by Yucaipa or other public stockholders.” […]