It was good, a solid 4 stars. There aren't really any flaws there isn't really a wow factor either. Tris is a well written character, the plot was gripping, the world building was interesting (although I do wish we got more backstory as to how they got to this point, since there's a few hints that it's futuristic.) 
Four reminds me of Warner a lot, if he was kinder and more controlled. Basically less traumatized. 

The only thing I didn't like about the book was how easily Tris brushed off the traumatic events that happened, which is one of the many things I appreciated about Six of Crows. In that book the characters have trauma from the stuff that's happening, meanwhile in Divergent when

she kills Will and is able to just "force herself" to forget. It just seems like the author didn't feel like diving into that, which would be ok if she didn't make the characters do these things or tackle mature topics.

 
In general I do recommend it and I'll probably read the rest (if purely because the series is short, any longer than four books and I wouldn't continue it), but it's not a new favorite.