Angels and Demons by Dan Brown is a great book! It seems like you might be reading it in school, which is really cool.
The genre of the book is mystery-thriller. I would describe the writing style as popular. The book is meant to be easily accessible to most readers and fun! This isn't esoteric or allegoric. I've occasionally heard the book described in a derrogatory fashion as an "airplane novel." Essentially, that it's so easy to read you could pick it up in the airport and be done by the time you land. The term is considered a bad thing, and I don't necessarily agree with it. Just because something is written in a way that's easy for most readers to appreciate, doesn't make it bad!
As you probably have experienced from reading it, the book is a page turner. It's a mystery, as Langdon and Vittoria follow the clues through Rome to try to save the cardinals who are being mysteriously killed. It's also a thriller, throwing suprises at you left and right! Like its companion, the Da Vinci Code, it's also full of puzzles, riddles, and references to secret societies and cults. And of course, all of this takes place in a race against the clock, just to ramp up the drama! All of this makes it more fun.
If I were you, I would focus on any scene in which Langdon is confronted with a puzzle he needs to solve as part of his race around Rome on the Path of Illumination to save the cardinals. Perhaps the scene in the Santa Maria della Vittoria would be best, as it highlights many of the aspects of Brown's style I've mentioned.