I know I didn't like The Da Vinci Code, but I was told to give this one a try. I didn't enjoy it for two main reasons, though it was fun to look more at art history (took a course in HS and kept up an interest since) and to buzz around Rome/Vatican City with the characters (visited these over Christmas).
Reason 1 = less important one. Amateur author. He lectures first to relay info, and then tries to couch it in plot and character development. No one purely lectures without a bias or a hope to show off/hide himself - a trade mark of personality. I am a psych student, so I can see how people speak for them selves more than their knowledge, and I do admit I am biased. Also, the bad guys are REALLY BAD and the good guys are REALLY GOOD and everyone else isn't all that memorable. This lacks sophistication. The most irksome point though is how two or three people will sit there and argue very elaborately for several pages DURING A CRISIS...GRRRR...my rm often laughed at how impatient I was and unforgiving of characters who are indecisive. But this is forgivable as it was his first novel...to my recollection...and he's already far better than others who have published.
Reason 2 = most important one. At around page 40 I realised what premises he has made in order to support his fantasies in the novel (as in making it fiction, not a fantasy fiction novel). If I could swallow these few statements re: his beliefs, then I can accept his story and be carried away by the novel for a time. Conventions...there we go, I can remember my HS drama classes now. Because he couched his conventions in the school of art history and of the history of science, I was struck by the permanence of his ideas. So either he was using his current mindset in order to re-interpret the past (a no-no for historians to do) or his mindset has an element of wisdom to it as it is so permanent. I chose the former, thus rejecting his premises and then rejected his book.
Essentially I figured his conventions weren't wise, and in rejecting them I rejected the illusions he created with his story...couldn't get into the book, and then couldn't enjoy it.