I loved it....
Plausibility aside, I loved this book for a few simple reasons:
(1) it is a wonderful "guilty pleasure" or great escapism;
(2) it is extremely fast-paced and fun/easy to read;
(3) I found it much more interesting than "DaVinci Code" and "Angles and Demons"; (4) it had the perfect amount of twists and turns, one of which completely shocked me;
(5) the ending truly satisfied me; and
(6) I walked away from it feeling I learned something new.
While at times I'll admit there was a little too much "teaching" for my taste, and I felt the author tried too hard to impress with the tremendous amount of research he had done, I really can't complain because of the six reasons I listed above. (And because I respect the fact that so much research and thought went into writing the novel.)
I highly recommend the book and am a bit surprised so many people didn't love it like I did. Therefore, I would recommend approaching it with an open mind and remembering its a work of fiction.