I really enjoyed this book, however, there were certain things that held me back from a 5 or even 4 star review. 
 First, the expectation was extremely high, as I had heard some really great reviews for it. So, obviously my expectations were not met and I was slightly disappointed. The story started out amazing, with mystery and suspense, and then it just kind of withered as it got closer to the second half of the book. 
 Second, the story was actually not what I wanted at all. I am a huge fan of magic, mystery, other worlds, puzzles and thrills. Yeah, this book had a secret society, yeah there was a puzzle, but those were not really the heart of the story. The secret society was just kind of there and the puzzle wasn't really presented in a way that had me trying to solve it. In fact, I kind of forgot at times what the character was trying to solve. I really enjoy interactive puzzles; something that has enough hints and clues presented so that I am building my own theories and proven wrong or leaving me wanting to go back and read it again so that I can connect everything to the resolution. This didn't really do that. 
 Third, yes I understood that it was meant to show a coming together of old and new, books and technology. But, the technology kind of got in my way of enjoying the story. Half the time, I didn't understand the concepts presented, as I am not quite as literate in the art of coding and whatnot. I also thought the absolute worship of Google and Kindles threw me off a little. 
 Fourth, I kind of hated the characters. I enjoyed the main character, but in all honesty, I never really got to the point where I felt like I knew him. Where was he from? What were his parents like? Did he have siblings? I could not stand Kat. She really bugged me and I thought she was sort of pointless toward the end of the book, basically non-existent. I liked Mat, but he wasn't in it much and wish he had been. My favorite character is still a mystery, Mr. Penumbra. I feel like there could have been so much to him and I am extremely disappointed that I didn't get to know him as much. 
 Lastly, and probably the biggest thing that I am disappointed about, was the lack of depth with the bookstore. A crazy, mysterious bookstore like that and its not even talked about except as a place that has tons of books? I wanted so much more than that!! The potential is astronomical!! Why wasn't there more?? 
 Alright, now that I have talked about what it lacked, I will say a few things that I really enjoyed. 
 I really liked the writing. Some people may be thrown off by it, but I enjoyed the different type of narration and felt like it is exactly how I think and talk in my head. I enjoyed that. I enjoyed the variety of characters, even if I was disappointed by the lack of detail surrounding them. I also appreciated the different ideas that came from the story. Lots of different places and exciting new things that were presented that I haven't seen in any other story before. 
 Overall, I enjoyed it, but I thought it was lacking. I thought there was so much potential and it just left me wanting more depth and more insight.