Cheboludo, I liked The Shining Girls. It's quite graphic in terms of the descriptions of the actual murders and the killer's sexual gratification during the acts, but not hugely extreme, compared to other crime novels and programmes like CSI etc. No-one is kept prisoner or tortured for extended periods- that's the kind of thing that gives me nightmares!
it's not really a suspense novel where someone is trying to escape the killer and you are constantly waiting for them to be caught. There are some other potentially upsetting themes in terms of animal cruelty and abortion, but very minor (occasional mention).
I chose it initially because I am professionally interested in the fate of the radium girls, but that was a minor part.
I also found the details about life in the US during the Great Depression etc interesting. I found the time travel aspect a bit confusing at first, but was an interesting concept - but as a rule I have no interest in fantasy and sci-fi themes.