NEW YORK — Caps and gowns are in fashion right now, and so, apparently, are copies of "Lean In" as a graduation gift.

Sheryl Sandberg's manifesto for women in the workplace will again top The New York Times' nonfiction best-seller list in the paper's June 16 edition. "Lean In" had last been No. 1 on the combined print and e-book list May 5.

Paul Bogaards, executive director of publicity for Alfred A. Knopf, said Thursday that sales have been especially strong lately because the book is a popular graduation gift. He said "Lean In" is now in its 15th printing and has sold 600,000 copies just three months after publication.

Sandberg, Facebook's chief operating officer, has been encouraging a national conversation on how women can advance in their careers.