Best/ Worst parts about book

I am about about a quarter of the way through "Divergent" by Veronica Roth. I am enjoying the book. So far there have multiple (but small) climaxes that help make the book captivating. One thing that I don't like about this book is that it takes a long time to really get into the book. I think this because I think I am pretty far into the the story, but nothing major has happened yet (my friend who has finished this book has informed me of this). I also don't like how the characters are introduced. There are many characters in this book, and a lot of them get a very small introduction. It can be difficult to imagine (and remember) them while reading. Other than these things, I really like the way the book is set up: setting, conflict, imagery, ect. The way Veronica Roth wrote this book makes room for lots of action and suspense.