I think the best thing about books is that sometimes, the really really good ones stay with me (especially the ones I read as a kid). But in some cases, that staying power can be haunting. In those cases, I get what I call reading regrets. It's when a book is so emotionally affecting or has such a troubling plot that I can't get it out of my head.
Reading regrets have nothing to do with the quality of the book. I have had reading regrets about beautifully written books. In fact, the few books about which I've had reading regrets are so well-crafted that the upsetting parts are particularly vivid. A good writer will help you really see a scene, but if that scene is violent or sad (or whatever else might push me over the edge) it stays in my mind's eye forever.
Some books hover just on the line of what is too much to take. I've read some about slavery, for example, where I really had to take a deep breath and push through (and not read it when I was feeling too tired or emotionally vulnerable!). But in the end, I learned something, and felt that it was my responsibility to toughen up to get through it.
The book about which I've most recently had reading regrets was an award-winning novel with a plot that was driven by a ceaseless series of violent acts—a few of which were just too much for me to bear. My memory of this book is tied up in all sorts of strange experiences: it was given to me by a friend who was cleaning out his bookshelf, and passed a big stack along because he knew I am a big reader. I worked my way through them, never choosing this particular book, and then my friend suddenly died.
This book was the last in the pile, and I took it on a family trip to Florida. We stayed in a hotel whose décor was based on a monkeys and palm trees theme. I remember reading this book in the room, surrounded by wallpaper, curtains, furniture and linens all featuring monkeys and palm trees—quietly reading this horrifying book with my daughter and family nearby.
Later on, I couldn't stop thinking about what I had read. It was a year and a half ago, and certain scenes still pop into my head and stun me, and I have to do some mental and emotional gymnastics to switch my train of thinking. And sometimes I wonder about my friend: why didn't he warn me? How could he just slip this in with a pile of beach-reads and best sellers?
I still wonder if it's fair to regret reading a book. I would never want the author to know, for instance! Sometimes I think it's just a matter of stamina, and whether imagery tends to stay with you. It does, with me.