After building Barnes & Noble from a single college bookstore into the largest book chain in the country, Len Riggio is retiring. Riggio, the founder and chairman of B&N, who's been heading the company since its inception in 1965, said he has "done everything I have wanted to do in business" and that he is now looking to focus on his "philanthropic and social" interests.

Riggio, who will step down in September, will stay on at B&N as a board member. Paul B. Guenther, former president of Paine Webber and a B&N board member since 2015, has been named by the board as non-executive chairman, to take over after Riggio leaves. Rob Boire, B&N CEO, will report to the board.

In a letter to B&N's staff, Riggio said the decision to leave came with "great difficulty" but that he is "at peace" with himself. He then added: "No one in the whole world of business could have had a career more fulfilling or more rewarding than I."

Riggio got into bookselling to help pay for his college tuition, taking a job at the NYU Bookstore. He told his employees that he fell in love with the profession immediately. "I never had a bad day when I worked in a bookstore; I never met a reader I didn’t love serving; I never knew another bookseller I didn’t admire and respect."

But B&N, which remains the largest bricks and mortar bookseller in the country, has faced immense pressure since the rise of e-books and the migration of bookselling online. Barnes & has struggled and the launch of the Nook, at first a success, has resulted in deep losses in recent years and the company has been drastically downsizing that part of the business.

In addition to starting the B&N trade stores, Riggio oversaw the growth of book superstores. Considered a visionary retailer, Riggio also created both Barnes & Noble College Bookstores (which was spun off from B&N last year as Barnes & Noble Education) , and GameStop, the country's largest video game retailer.

Despite the new challenges, Riggio, who will remain B&N's largest shareholder, remains confident that the company can continue to be a major force in bookselling. Things at the company, and in bookselling in general, "have settled down," he said. With the scaling back of its digital business B&N "will get back to what we do best—retailing and selling books," Riggio told PW.

Well known for his philanthropic efforts, Riggio, has been a longtime champion of public education, literacy and civil rights. Among other things, he supported the building of Beacon, N.Y.'s contemporary art museum Dia: Beacon (a dedicated building is named Riggio Galleries); helped create the Langston Hughes Library on the ground of the Alex Haley Farm in Tennessee (where there stands the Riggio-Lynch Chapel); and has established numerous scholarships and fellowships. His efforts in this area have also earned him numerous awards, including the Americanism Award from the Anti-Defamation League and the Frederick Douglass Medallion.