Namely, the way an author introduces graphic content, or topics of more sensitive nature. This could and likely would include torture, rape, child abuse, experimentation of any kind, gore, severe violence, and the list could go on forever.
Many authors seem to think that putting such things on the first chapter, first page, even first sentence, is a good way to hook a reader. In some ways, this could be true. It does create instant sympathy for the victim, or instant hatred for the perpetrator. But it's more of a Russian roulette. Chances are very high that doing so creates an opposite effect. It is a very bad idea to alienate your audience.
Commercial break: One rule of thumb that applies to anything a writer does... if it turns off the reader(s), don't do it. Period.
Now let me be very clear. I am not saying to avoid writing on such topics. On the contrary, if a story demands less than pleasant situations in order to drive your characters to their best, so be it.
But learn to use good timing.
Let me explain by comparing two books which deal with nearly the same situation. I've read the book "Hunter of Worlds" by C.J. Cherryth and attempted "Stewards of the Flame" by Syliva Engdahl.
Both of these books have an MC who is abruptly taken by a group in power, and various alterations, indignities, and implants are done to them. Unwilling. (this may not bother some people, but it does me) Both authors deal with the same somewhat uncomfortable topic, but I only managed to finish one book--Cherryth's book; the other filled me with nausea.
Why the difference? How the author handled it. Cherryth timed her revelation of the unpleasant situations carefully, in a manner that gave me (the reader) the ability to handle and finish the book. Engdahl, though one of my favorite YA writers, did not, in my opinion.
Here's three things I've noticed. I consider them general guidelines, at least in my experience as a reader and a writer.
1. Do not start with the uncomfortable/frightening/graphic topic. Not in the first paragraph, not on the first page. I'll go so far as to say, not even in the first chapter.
Once you create a knee-jerk reaction, it is extremely difficult to overcome a reader's "eww" response. Books tend to end up back on bookstore shelves.
In Cherryth's book, the alterations and etc are performed in the third chapter. Engdahl's work has it within the first five pages or so.
2. Foreshadowing is your friend. If you are going to introduce a hard-to-swallow topic, make sure you give the reader ample preparation. It is easier to handle something that I'm prepared for than to have it thrust upon me.
Being prepared for a flu shot...being jabbed unexpectedly by a needle. Big difference between the two, isn't there?
Both books do possess foreshadowing, hints of things to come, but the pacing is all wrong. Engdahl has only a handful of hints before the dreaded events begin. Since there is very little time for the foreshadowing to unfold, I was more appalled, shocked, and disgusted than anything else.
Three chapters in the other book gives a great deal of room. By the time it happened, though I didn't enjoy it per say, I was more saddened and concerned for the character.
3. Build a relationship between character(s) and reader. If all a reader has is a name, maybe a general face, and then abruptly that character is running from a rapist, it is very hard for me to continue reading, to put myself through that rough/painful scene for a character I don't even know.
On the other hand, if I've seen this character be kind to a young child, seen some of his/her hopes and dreams, care for an elderly relative, etc, and now they're running from a rapist--now I care, I want to read to see how the character escapes.
Make me care about the character and I'll be willing to follow wherever the story leads.
To sum up, check out this video. This circus act only works because of one thing.