This was a lot of fun to read! It was kind of a little bit National Treasure meets meets The Librarians and I really liked that. I mean there's a secret group trying to solve an ancient mystery in books- how could it not be great. This was very well crafted and all of the characters are well thought out and advance the plot in some ways (this is weirdly rare and I wish more books would do this). I wasn't crazy about the way the main character had these asides and kind of talked to himself at some points, which is why this wasn't a 5 star book, but otherwise I really enjoyed this. Basically if you love mysteries and books and history and codes, this is going to be something you'll likely enjoy a lot. This is a book that you can't put down once you get into it.