This was a case of wrong author for this series. I am not sure if Baldacci had even read one book in the 39 Clues series. The characters were all horrible and came across as if he were handed a list of characteristics and important points and that is all he did with them. 
 The conversations between the characters was stilted and horrible. It felt like watching a horrible movie with bad acting. 
 An average conversation would go like this - 
 Character A: OMG! I think I got it. Like, I was just thinking and we could _______ (insert action). 
 Character B: What do you mean _________ (insert question about said action)? 
 Character A: (Gives lengthy explanation about said action which is very basic and considering the characters are so smart would already know). 
 Character B: I don't know, like, what if it didn't work. 
 Then there was this horrible, forced romance. Amy - who has been really level headed- makes sure to spend most of her time 'OMG' her hot travel companion (which she hadn't done in 5 books). And of course the world is ending so she and her hot travel companion make sure to snog and make lovely doey eyes at each other almost every page of the book. 
 It was just a horrible experience all around.