Overall, I thought the book was okay. It started and ended as an action novel with the same standby professor that wants to be Indiana Jones. I've the read all of the others and I don't generally read these books for the characters or the action. I read them for how the art and history is tied into the work of fiction in a bright and interesting way. It's like reading really bad science fiction for the ideas even though the writing stinks. 
 As I started reading it I groaned and mentioned to my wife that it's coming again: A psychopath is going to be fixated on an idea again and it's going to cause huge problems for the whole world. Only a historian will be able to save us all! 
 People mention formulaic writing and often say it's a bad thing. It's not. Not really. 
 We had the first half of the book being colored within the lines and then Mr. Brown decided to scribble his crayon all over the page. He consciously decided to break his formulaic prose, and while I can respect it in theory, I almost put the book down because I was so conscious and annoyed with what the author was doing and my credulity was stretched so damn far that it really almost broke. That's saying a lot for someone who has no problem with quantum sized people living on the corona of a neutron star deciding whether or not the want to join the mass human exodus through a naked galaxy-wide singularity. But I digress. A 180 of the main players is fine in a novel if it is apparent to the reader that it was planned for, set-up, and otherwise jammed down our throats in at least a modicum of foreshadowing. I was reminded of how it was done very well in the movie called The Game directed by Fincher, and was not favorably disposed to the execution in this novel. 
 A novel-wide Oh By The Way is the surest way to prevent yourself from being published, and I have to say that this one was one hell of a whopper that seemed to have been called for not because the plot required it, but because the author either didn't know how to get to where he wanted to be at the end or didn't like how the first write was progressing and didn't want or couldn't have a rewrite. Maybe it was shot through the publishing industry so fast or without an editor or perhaps several conflicting editors. Whatever the reason, I pulled on my hair and rolled my eyes and wanted to throw the book across the room. 
 Since I don't throw books and if I start one that I don't particularly want to read anymore, I still read them through, I continued the novel. And it was okay, all the way to he end. (Granted, by that whopper, I wanted the plague to wipe out humanity and I was really rooting for the bad guy and wanted to see what Robert Langdon was going to do in the next novel with a disease-ridden humanity, a post-apocalypse setting. Alas.) 
 So, hooooooboy, Mr. Brown broke the formula and there aren't any bad-guys, despite the pretty decent setup and reasoning FOR the bad-guys. Ahem. The formula sells, and it's fine to break it as long as you've got a dedicated readership. The problem comes when the reader's trust is also broken. If you don't want bad guys, don't sell us bad guys. Sell us a morally-grey soup and lead us through the maze. Don't advertise a bill of sale in the first few pages and then turn a bait-and-switch in the middle of the novel. 
 Still, the whole novel was pretty alright. If only I could get over this sense of betrayal.