Brandywine Books asked some bloggers if "it's appropriate to ignore or scan parts of a book which you review?"
Here is what they said.
I myself feel honor-bound to read a book I'm reviewing all the way through. Since I write a column designed to recommend books, I don't have to finish one I don't like anyway. But from time to time I have to read a book I don't think is very good -- and even some of those I recommend are not without faults. The Da Vinci Code is bad, but it goes through one eye and out the other, so it's no great effort to read, just not very rewarding -- in fact, totally unrewarding. But I remember reading a book a few years back that had patches of such dull incomprehensibility that I might as well not have read them, given that I got nothing out of them.