It's amazing. If you didn't know, there's two more books and the series is finished.
You should also watch the movie. I'm usually disappointed by movie adaptions, but this movie is perhaps even better than the book.
The series as a whole also has an ending that kind of...makes you think...and have a mix of emotions. Like all good books should.
Also, I just loved the character development that went into Tris, and being with her as she grew throughout the series and came to terms with being Divergent, and realizing that she didn't JUST have to be abnegation, or dauntless, was a good thing to see.
I stuck in one of my favourite quotes from the series which shows how she came to terms with being both abnegation and dauntless, but is also just a brilliant quote that shows her character. If you struggle with the ending of the series like I did, try to think of this quote in regards to said ending, and you'll understand it better.