I was up all night with the first book (Divergent) and ended up having fever the next morning.. that reminds me of my sleepless nights with Harry Potter books (the Order of the Phoenix was the first book of the series I ever read). While I actually finished Divergent in that one night, I needed more time to finish The hella thick Order of the Phoenix (and also the next two books in the series).
Reading Divergent, I found myself wondering which faction I would choose. And since I was a potterhead myself (got to say, cause I'm no longer in touch with it since the last movie), I found it (the faction system) is quite similar to the houses in Hogwarts (Gryffindor, Ravenclaw, Hufflepuff, and Slytherin). What makes it different is, in Hogwarts, the house to join is chosen (or announced) by the Sorting Hat (citing Harry Potter Wiki : It seems that the Sorting Hat tends to place students based on qualities they value). Whereas, the faction is something people (not student) can choose, although there is this so-called aptitude test to find out which faction suits them best. After the aptitude test, there is this Initiation, another test to get through before someone can be part of the faction.
In the Divergent, there is another part of the society called the Factionless. Yes, for those who has no faction. What we've got in Harry Potter? Squib? And Muggles? Both can't perform magic, both won't get invitation from Hogwarts. Well, back to Divergent; the Factionless is for those who failed the aptitude test or the initiation.
That's all I can relate, for conflicts and plots it's totally different.
P.S. ALLEGIANT (#3) is about to hit the bookstores! Expected to be on October 22th. Can't wait!!