Do you read the inside flaps that describe a book before or while reading it?
I try and only read books that I’m already interested in or have been recommended to me–it saves me a lot of heartbreak over bad books! But I do read the inside flaps (or back covers) before reading, especially when I’m picking through a bookstore. If a premise or plot grabs me, I add it to my list. But while I’m reading a book, I tend to ignore the flap or back cover in favor of actually reading the book.
The most useful thing on the flap (or back cover) for me are the quotes from critics and other authors. I picked up Sunshine because there’s glowing praise from Neil Gaiman on the cover. If I’m unsure about a book, I use my time-tested strategy to determine whether it’s worth a shot or not. (This also works for DVDs, incidentally.) I check the sources of the quotes–if they’re authors I like or big name newspapers, the book will, most likely, at least be decent. If the sources are very local or only authors in the same genre, I tend to give it a pass. It’s worked well for me over the years.