One problem I found with this book is that it is too overwhelming for the reader. I mean, it talks about so many conspiratorial theories and prophecies as to keep pace with all of them, so the final result is a non-understandable mess. I got lost lots of times while reading the book. Besides, there are so many things happening at the same time, with so many characters and settings, that it can get really confusing.
One big problem. I am Spanish. This book is set in Spain. I didn't like how Spain was portrayed, and it definitely shows that the author should have done a bit more of research on Spain before daring writing a book set in a country that he obviously doesn't know. I won't say more in order not to include spoilers, but I will just say this: a Spanish monk that speaks perfect English? No, you won't find such a person here in Spain. Unfortunately, English has never been so popular here, so almost nobody can speak more than two sentences in that language. As far as the Gibraltar part is concerned... well, I won't say anything about that or this review will never end.
The characters are flat and they don't show any development. What is more, all of them have the same voice and that's not good. I mean, you cannot make a historian and a smuggler to have the same voice and use the same vocabulary and expressions. About the main characters, they are not coherent with the rest of the story. Their behaviour and dialogues don't really go with the events that are taking place.
As for the plot, it is too messed up. There are too many things to deal with, too many characters to remember, and a bunch of theories that shouldn't appear all together. It's just too much. I think this book would have worked better if the author had chosen just one conspiracy theory and had fully developed it. Just as it is, the book gets too boring; my mind used to go wandering around when reaching certain parts of the book. The book ends in a cliffhanger, since there is a second book... I won't read it.
It is a pity, because I started reading this book with high expectations. However, I really think that with a couple of more edits, this book can improve a lot.