A letdown, like most of his books. I have read four of them now, including Inferno. And except Angels & Demons, which I consider his magnum opus, all of them were mediocre at best. All of them pulp, of course, but pulp can still be entertaining.
Digital Fortress was awful. I guess it was for anyone familiar with cryptography and computers as painful as his Robert Langdon books must be for art historians. Just really, really bad. Da Vinci Code was OK, but the whole story just too over-the-top for me. Angels & Demons was amazing. Something about it just clicked with me and I love this book. That lead me to read Inferno and left me rather disappointed. I shouldn't complain, I guess, because it is a typical Dan Brown. It just didn't click, like A&D did.