BLURB. The back-of-book description. A short promotional piece accompanying a creative work. Whatever you call your book summary, it's an important element of your book to attract readers to read more.
Make your BLURB short and descriptive. Make it dramatic. They don't want the length, they want the drama, the tension. They want to know they're going to dip into a world where they're hooked and curious and completely immersed till the end. If your blurb doesn't hook your readers, they're going to assume your book won't hook them either.
So, get ready Wusters! Look at the picture.