Both Amazon and Apple don't allow much space, so if your text is too long, it will be cut off and the reader will have to click "read more" to see the rest.
What makes my book different? Well, a blurb is also a tagline that is meant to sell a product—your book. The back of the book cover and blurb of course.
Many self-published authors try to squeeze too much into their blurbs. In a refreshingly entertaining how-to guide … Jen Sincero serves up 27 bite-sized chapters … helping you to: Identify and change the self-sabotaging beliefs and behaviors that stop you from getting what you want.
Long and convoluted sentences, jargon, specialized terminology—all make the blurb appear complicated and limit the readership. First, Edward was a vampire.
Unable to keep it to herself, Rachel offers what she knows to the police, and becomes inextricably entwined in what happens next, as well as in the lives of everyone involved.
The key is to imply similarities between comparable books without sounding derivative: ensure you also distinguish what makes your book unique.