How to get more atlas passives?

I've completed the quest from T1-15 maps, so where do i go from here? I've gotten some books off of some map bosses which increases the boss levels but that's about it.

Is there a way to get more atlas points?

You get them by killing map bosses in maps with higher and higher area levels. You can get a total of 30 points. The last 2 you get from an area level 82 map boss (t16 waystone + corruption + irradiated). It tells you the number of points you have and the method for getting more when you mouse over the bottom of the atlas tree (where it says x/30 points)