The year before I started at the GSB, a favorite Professor actually ended his commencement speech reminding students of this. The thought process, "Oh I shouldn't do this, but I've already invested so much in to it I might as well finish it." is surprisingly common, very human and completely wrong.
So as I finished about half of Brida by Paulo Coelho, whose novel The Alchemist I'd absolutely loved year ago, I had a decision to make. Would I, for the very first time, deliberately abandon a novel?
It wasn't a bad novel, but it hadn't gripped me and wasn't really teaching me much or making me think of anything new. It's not a bad book, just not a great one. While as most of my friends know my standards for movies and TV are pretty low (I'll cheerfully watch almost anything), it turns out my standards for books are a trifle higher.
I'm abandoning it; later tonight I'll probably read the last few pages; I like to know how things end but that'll be it. I just got started on this one (Yes!: 50 Scientifically Proven Ways to be Persuasive), and its entertaining so far; more later.