Every three months I've been looking at Barnes & Noble's quarterly conference call to get some insight into recent book industry trends and to see which books were the big sellers over the past few months and which are expected to be big in the coming months. Barnes & Noble's first quarter ended May 5th. Here are the highlights from CEO Steve Riggio on the Q1 conference call (courtesy Seeking Alpha):In keeping with an ongoing trend, Barnes & Noble's margins were pressured as the chain continues to discount heavily to stave off competition from the likes of Wal-Mart and from Amazon's popular Amazon Prime program. Nonetheless, Wall Street seemed to like the overall numbers and pushed the stock higher.Sales in both the stores and online were better than expected. "Both benefited from a better new release schedule than we've seen in some time.""Rhonda Byrne's The Secret has the unique distinction of being our bestselling title in hardcover, audio book and DVD."Riggio said that Mohsin Hamid's The Reluctant Fundamentalist was the third straight "Barnes & Noble Recommends" selection to "become an instant fiction bestseller upon publication."Meanwhile, Oprah drove sales of Sydney Poitier's Measure of a Man and Cormac McCarthy's The Road.The quarter's non-fiction bestsellers were Einstein by Walter Isaacson and In an Instant by Bob Woodruff.Looking ahead, Harry Potter and the Deathly Hallows will hit the shelves at the end of Barnes & Noble's Q2. Khaled Hosseini's A Thousand Splendid Suns just debuted "with very strong sales." There's also new fiction on the way from James Patterson, Nora Roberts, Robert Parker, and Ian McEwen (On Chesil Beach).On the non-fiction side of the ledger, new release The Reagan Diaries is already selling well. A pair of books on Hillary Clinton are coming shortly: A Woman in Charge by Carl Bernstein and Her Way by Jeff Garth. "We expect, of course, many more titles by and about the candidates for the presidential election season to be coming over the next year to 15 months," Riggio said.