@wickermanstudios
I want to see them used more, but I've been wondering how to include them within the pages of a book as they can be spoilers. The other day I was musing on a 'Content Warning' Warning page xD
" The following page lists some things that some readers would like to know about in advance. They may include story spoilers. You may skip the next page as desired."
Or something like that. I almost certainly will have some for my book due to gun violence, sexual violence, etc.