Ok, so I finished this a little while ago but needed some space before I wrote about it.
My review in basic terms is that it did what was always going to do, tell an entertaining tale with no groundbreaking surprises. I liken reading a Dan Brown book to going to see the next installment of an Indiana Jones movie. It's not (or shouldn't) going to win awards and it's not going to stretch your mind, but it is going to entertain you if you let it.
Ok, so the "Big Twist" was so fricken obvious that he might as well have printed it on the page halfway through the book instead of the end. And yes, the one time it surprises you and you think "Wow! What a great twist!" it turns out to not be a twist and lets you down. But the fact is, you read it. You enjoyed it. Now put it on the "glad I read it, now I can forget about it" pile and and move on.
DO NOT start posting on anti-Freemason sites.
DO NOT start trying to join the Freemasons.
DO NOT start searching for the Masonic Pyramid.
It wasn't that good a book.