You will always dow a short preview of say one minute, just to know in general what the book is about, fiction, non fictions, story about...?
I've picked up books thinking cool, interesting title I'll photoread that and on a in a 60 second preview discover it's a subject far removed form anything I'm ever going to be interested in. Remember the old saying "you can't judge a book by it's cover"? well it holds true today even more thanks to mass marketing.
Alex