Huh. As a reader of mysteries, I found it fast moving and quite interesting. His plot was far more complex than most of the mysteries written, but flowed a lot better than did Angels and Demons.
As for his ending, I do think that served two possible purposes. First, while building what most here consider an anti-Christian theme, his protagonist saw that whatever documents were there might endanger the Church and did not want that. And second, let's face it, makes for a great sequel....
The blatant errors (guns transmuting between revolvers and self-loaders, other spoiler-related goofs) and total fiction in that book leave me with no temptation to read this one!
Plus, there's been enough presented in the popular press about the idiocy of this one (more blatant poor scholarship) that I'd guess only the very ignorant would expect much of it other than a thinly disguised fiction. Am I right?