Its a combination of good writing on human behaviour and the actors portrayal of a psychologically disturbed character.
::nods a lot::

I'll proceed with caution on Jessica Jones. I usually stop watching shows if they get too explicit with any forms of violence or trauma.
There was a Tumblr post talking about it... As far as I remember, if you're OK with episode 1, you should be fine with the rest. But it *is* disturbing and dark.