IYO, is there a difference between DNF and deciding a book is not for you?
Ill speak from personal belief, because I don't know a better way to explain. Whenever I pick up a new book (physical, electronic, or audio) I gave myself between 3 - 6 chapters to decide if I like it. If during that stretch I am not engaged or interested I move on. But I do not consider this not finishing a book. I think about it more like watching episode one of a TV show. Ive barely started, just enough to know I won't enjoy it. To me actually not finishing a book comes when I have invested and then actively decide to stop engaging with the story. Its rare for me to engage in a story and then suddenly not want to finish that story.
Thoughts? Do you have an exit ramp for books, and if so when? When is your point of claiming not fininshed vs not interested?