It's not all darkness, and sometimes it's just a tone more than plot for me.
But as someone else said (and better than this), you have to have the darkness in order to appreciate the light happy things.
As for being triggery, well it's helped me because I know that whatever demons there are in the world, we all share some of them. And as a bonus, here is someone who has lived through them, wrote about them and in a way relived it all, and is pretty damn okay. It's a good reminder that I don't always have to fall apart when I feel like I am.
Just my little opinion.