This is my own literary snobbery shining through, of course, but I honestly find Dan Brown to be largely unreadable, and I say that as someone who's made it through The Da Vinci Code, Angels & Demons, and The Lost Symbol -- the first out of curiosity, the second to see if it could get any worse (it did), and the third thanks to a bet.
His writing style grates against me like few others'; here's a simplified log of his various offenses: http://www.telegraph.co.uk/culture/books/booknews/6194031/The-Lost-Symbol-and-The-Da-Vinci-Code-author-Dan-Browns-20-worst-sentences.html My favorite take-down of Brown can be found at http://itre.cis.upenn.edu/~myl/languagelog/archives/000844.html
I don't find any reward in solving his "mysteries," with their massive plot-holes and increasingly obvious conclusions. Personally, give me a real historical puzzle-thriller like Eco's The Name of the Rose any day. Even Caldwell and Thomason's The Rule of Four, which is probably more to the liking of Brown fans than Eco would be, is a huge step above.