Reading lust-i know willingly reading and enjoying impure stuff is a mortal sin, but when your reading something impure and you dont want to look away, but you try to be careful and block out bad stuff is it still mortal sin.
Dirty thoughts-I know if you entertain dirty thoughts its mortal sin, but what if you provoke them, but your repented as soon as they come in your head and try to kick them out, or maybe you look for a milasecond, then try to kick them out
Part 1: This kinda depends on the circumstances. If you are required to read something dirty, as in a homework assignment (I had to, since I’m in college and took and intro to fiction class), I would say go with what your proposed and just bite the bullet through the bad parts. But if you can avoid it by your own free will, I would say do it. I once tried to play a computer game even though it had racy content in it, and I tried to ignore it, but I jsut felt like I was trying to justify a sin. I eventually decided it was more trouble than it’s worth and stopped playing altogether.
Part 2: Yes, you cannot sin if you willingly resist impure thoughts. They are not sinful if they merely pop into your head. Think of them as flies that you need to swat away.
First situation - It depends on if you are required to read the book or not. If I might encourage in doing some spiritual reading instead.
Second situation - If you keep rejecting those thoughts then that is a good thing. I would just confess to a priest that you are having a problem of entertaining thoughts that are dirty even though you are doing your level best to reject them. When you find yourself thinkging these thoughts, look at a crucifix or say a Hail Mary. It is hard to keep entertaining these thoughts when one is thinking of God thoughts.
Someone once told me to pray 3 Hail Mary’s in asking her to help me to keep chaste, and I have, and it helps very, very, much.
My Spritual director tells me that the battle is fought in our thoughts. When we have thoughts come in, we cannot control them, we can reject them and choose to think of other things. We need to replace these thoughts with good thoughts, hence thinking instead of spiritual matters when these intrusive thougthts come up.
Whether it be mortal sin or not, that is not for me to say. I can say it is a sin in some form.