When it comes to publicity, being denied entry into the United States may be the best thing that ever happened to Sebastian Horsley, right, unless you count being hung on a cross in the Philippines. Mr. Horsley, the British author of “Dandy in the Underworld” (Harper Perennial) — a rollicking memoir of his rampant drug use, abundant encounters with prostitutes and that trip to the Philippines to be crucified for an art exhibition — was turned back at Newark Liberty International Airport last month on the grounds of “moral turpitude.” He was here for a book party and media tour. Now PEN American Center, the writers’ organization, has invited Mr. Horsley to speak at its annual festival of international literature at the end of this month and written a letter to Secretary of State Condoleezza Rice and Homeland Security Secretary Michael Chertoff, asking them to admit Mr. Horsley to the country. Francine Prose, president of PEN American Center, said that Mr. Horsley was not originally invited as a speaker, but that his deportation made him a cause célèbre. “PEN supports freedom of speech and freedom of expression on the most basic level,” she said. “Writers should be able to enter our country regardless of what they’ve written.” Mr. Horsley, in a telephone interview from London, said he would “absolutely” accept PEN’s invitation if American authorities would let him into the country. “The pen is mightier than the sword,” he said. “And it’s considerably easier to write with.” So far his book has sold only a thousand copies in the United States, according to Nielsen BookScan, which tracks about 70 percent of retail sales.