@f this happens to me sometimes regardless of what I’m reading. I could be a novels, papers, anything. I’ve notice it happens mostly if:
1. I’m tired,
2. I’ve got something else occupying my thoughts, or
3. The material is boring
Sometimes, I’ll even reread the same page several times before I decide I should probably give up.
@f it’s been happening to me for a while. The first time I remember noticing it, was in 9th grade English class, when I was forced to read “classic” novels I had zero interest in.