NASHUA, N.H. (AP) – Dan Brown went from teaching books at Phillips Exeter Academy to writing them.

The former English teacher’s fourth thriller, “The Da Vinci Code,” debuted at No. 1 on The New York Times best seller list – a rare accomplishment for a newer writer. The novel sold more copies in its first two days, about 8,000, than any of Brown’s previous books had sold in hardcover.

More than 50 people went to Nashua’s Borders Bookstore recently to hear Brown talk about his books and sign copies. Fans raved about the latest novel, enjoying everything from its artistic puzzles to its tales of espionage.

“It’s just a great book,” said Joshua Dresner of Nashua. “I liked the secret societies, secret assassins … that’s what brought me in.”

The novel focuses on a Harvard professor who investigates a murder at the Louvre Museum. Brown said he spends a year researching and another year writing each book.

“There are plenty of nonfiction books about these subjects, but not many novels,” Brown told the crowd. “Many people aren’t familiar with them – when you’re looking for a beach book, you don’t look for a historical tome on the Catholic Church.”

His earlier thrillers also focus on real-world events. “Digital Fortress” was inspired after a 14-year-old at Phillips Exeter Academy was questioned by the Secret Service for threatening the president in a private e-mail, leading Brown to questions about privacy, codes and security.