While there are multiple depths to talk about when it comes to discipline,
@Sardi did make a point by mentioning it.
The brain ALWAYS wants to stay in a comfort zone. Whenever you bring something new it will make not do it. You just have to get past that.
It's a bit more complicated than that, and I could write about this for hours. But you might want to look it up and see what the issue is.
Whenever you feel frustrated, or agitated when about to start something, always remind yourself it will pass after around 4 minutes. Usually, that adrenaline/epinephrine you get when you don't want to do something but do it anyway, converts into dopamine and after a few minutes, it will actually make you enjoy doing it.
Regret weighs more than effort.
Now that I've said that, while I do agree some books need to be read, I really wouldn't go about reading whatever I can find just so I can read something.
I would more easily read 5 books about someone in the past, so I can learn something, rather than some novel.
Whenever you dislike something, try to change your internal representation about it.
"Boy, I need to read for the next 5 hours. That sure sucks, I rather go play pokemon go" can be "For the next 5 hours, I'll educate myself about <x> topic, so I can get a bigger raise/promotion/whatever. This sure is smart, I'll thank me later"