Four is from well Fours perspective, I would wait to read it until you finish the other three but if you really can't wait I would recommend reading it after Insurgent. Btw it does have a fair amount of romance in it.
Divergent is a series about a society divided among assigned factions and a girl who doesn't fit into any of them. The moral force of the books lies in the constant reminder that you should always, under all circumstances, make decisions for yourself, rather than letting society dictate these decisions to you
