I’ve been thinking about something along these lines. One example might be that the book contains a lot of information that you already know. In that case, skimming through might tell you which chapters or sections to skip, instead of having to read lots of stuff that you already know, or worse yet, get discouraged by the repetition of things known to you and never finishing the book, thus missing out on the good stuff that was “hidden” in the later parts of the book.

But as of yet I tend to read books cover to cover and either finish them or give up on them along the way. But I do take notes about interesting things, and sometimes I do little experiments with them also. My notes are a bit lazy in that often my notes consist of taking a picture with my phone, but I categorize the photos into certain albums.