Unless a book shows an actual lack of skill or intelligence behind it, I will persist and finish it, because many of my favorite books are books I didn't realize were as amazing as they are until I got quite a distance into them.
Skipping few pages always helps. Sometimes some concepts are hard to chew through. Black Swan in my opinion is a great book!
I didn't say that I stop if I find a book difficult. I stop if I decide that I don't like the book. But you're right, some times skipping some pages can get you going again with a dry spot in a novel.
(And I wasn't commenting on Black Swan, just on the concept of not finishing a book. I'm unfamiliar with Black Swan.)
I'm not only willing, I'm eager to give up on a book I don't either enjoy or find interesting. But I know a surprising number of people who force themselves to finish any book that they start.