I'll read book blurbs to find out about a book, but I never read the brief excerpts that are usually added to the front pages of a book, and I never read the new book teasers that are included at the end of the book.
The first because I don't want to know what exactly is going to happen, and also because a lot of the times it'll be a scene about a romantic clinch that really is only a small aspect of the story.
The second because if I read the teaser, then when I finally realize there is a new book out, and start to read it, I wind up thinking that I read it already because I'm familiar with the opening chapter(s).
I only skim a book if it's only been able to mildly hold my interest and I just want to find out how it ends. I'm reading one like that now - Janni Neill's first Allegra Fairweather mystery. I'm finding that I don't care about the main character, I think the premise of her hunky guardian angel annoying, and the characters' dialog and behaviors are just too rote.