Brown joined actors Tom Hanks and Ewan McGregor and director Ron Howard at Rome's auditorium to screen the film, which has already sparked controversy over Howard's charge that the Vatican interfered with getting film permits to shoot scenes in Rome.
Angels & Demons features Harvard symbologist Robert Langdon of "The Da Vinci Code" fame, played by Hanks. In the film, the Vatican turns to Langdon after an ancient secret brotherhood called the Illuminati kidnap four cardinals considered front-runners to be the next pope, and threaten to kill one an hour and then explode a bomb at the Vatican.
On Sunday, Howard said the Vatican had interfered with his efforts to get permits to shoot some scenes, a charge the Vatican said was a publicity stunt. Much of the film was shot on sets that painstakingly recreated the interiors of the Sistine Chapel and other famous Roman church landmarks.
Top church officials strongly objected to "The Da Vinci Code" because it was based on the idea that Jesus married and fathered children and depicted the conservative Catholic movement, Opus Dei, as a murderous cult.
CBS News correspondent Allen Pizzey reports "The Da Vinci Code" so offended the Church that there were calls for Catholics to boycott it.
The official Vatican spokesman said there would be no comment on "Angels & Demons," because "we don't want to give these people any more publicity."
Publicity for the new film around the Vatican has been confined mostly to posters on busses, reports Pizzey. The Vatican denies it asked that no posters be put up near churches.
Hanks says "Angels & Demons" is a much more fast-paced film than "The Da Vinci Code," which took in more than $750 million worldwide.
"This is like bang, bang, bang! There's no time for anything," Hanks said before the screening. "I like it because the circumstances are familiar but the form is very, very different."
Brown, for his part, said he never expected any of the success.
"I wrote the books that I felt like reading, really," he said. "And hoped some people shared my taste and apparently some people have. It's very fortunate."