The author of the book 'The Virtue of Selfishness' is Ayn Rand, a four-letter word that is the solution to the crossword. Ayn Rand was a Russian-American novelist, philosopher, playwright, and screenwriter. She is known for her two best-selling novels, The Fountainhead and Atlas Shrugged, and for developing a philosophical system she called Objectivism. Her book 'The Virtue of Selfishness' is a collection of essays that promote her philosophy of rational selfishness.