For me there's a couple things. I hate to say this but I always judge a book by its cover. If it obviously didn't have any thought put into it I am less likely to read the synopsis. Like the Alien books by Gina Koch (spelling?) Another thing is like in Malazan where it feels like you completely missed chapters but it was really just the author dropping you in. This works sometimes like in A Darker Shade of Magic, Game of Thrones, but wouldn't work in a book like Lord of the Rings or Assassin's Apprentice.