To this day I often have the same "problem" your mother had. Certain types of writing encourage it more than others. If the writing is too accessible and the pace too great I may be too involved in the author's detail to explore the story universe. Other times I feel forced to enter into the story universe in this way, to try to make sense of it, or to make sense of the characters in it, and being forced can take some of the pleasure from it. But when the writing encourages you to explore on your own, choosing your own points of interest—that is always a joy.