Reading a book is an act of self-derangement.
When you read, the voice in your head that you live with every day, ostensibly your own, is displaced, for a time, in favor of the voice of another. This voice can be friendly, or hostile; cold and dictatorial, or warm and humanist. Just as some people are incompatible and fill each other with antipathy, and should not be seated next to one another at a party, so some writers should be avoided as bad company. This is not a reflection on them, or, for that matter, on yourself, as some people simply don't get along, and may be perfectly fine human beings otherwise. In the same way, there may be authors that you like to have in your head, who, in the heads of others, fill them with dread and despair.
The things that you like about your favorite author may be the things that cause others to throw the book across the room in disgust. There is, as they say, no accounting for taste.
Having said that, even if their values completely contradict your own, it can be useful, for a time, to deliberately take on the mask of another's incompatible personality, to stretch the boundaries of what you consider to be yourself. This exercise, though uncomfortable, can only be usefully accomplished by reading books you don't necessarily "like." Or "understand."
This intentional mental weight-lifting could be likened to taking a hit of salvia, or DMT. It isn't necessarily "fun" per se, but it can be instructive, providing we approach it with an open and flexible mind.
The feelings of repulsion you experience when reading a so-called difficult book may have nothing to do with the content. You are taking into you a small piece of another person's mental DNA. His or her voice, way of seeing the world, and the inhabitants of his or her mind, regardless of what actually "happens" (in, say, a work of fiction), may arouse the immune system of your mind (that is, of your ego) which is designed to keep you in a state of equilibrium. Something about the picture this author paints of the world disturbs that equilibrium, challenges your assumptions.
Notice this. As uncomfortable as you might feel, you will probably not die.
Deep content may be dredged up, and where there is defensiveness, there is often hurt, or fear, or sadness. Again, notice this. You might not have even been aware that you felt this way, since the immune system has kept these issues well protected and hidden. If you are able to trace back the defenses into the darkness, you may find out very important information about yourself, and about what you assume the world to be.
Afterwards, you may need a little something to soothe your inflamed mind. I've always been fond of Neil Gaiman, or Mark Helprin, but your salve might be quite different. Regardless, be gentle with yourself. You've worked hard. Just as you wouldn't work out everyday, you wouldn't read difficult books everyday. Be kind.