on Kobo Writing Life:

In the publishing world, descriptions found on the back of a book or on an online page are often referred to as ‘blurbs.’ Reviews and testimonials are often also included in book descriptions, and are also referred to as blurbs within the industry. For the purposes of this article, I’m using the blurb reference to mean book descriptions.

Now that I’ve cleared up semantics, I cannot stress this enough: blurbs can decisively make or break your novel. Blurbs can be the difference between sales success and stagnation, eminence or anonymity. Why is that? The answer is simple: a book’s cover, title, and blurb are the initial factors a reader considers when making the decision to purchase a book. Consideration of price and reader reviews come shortly after, as a process of rationalizing initial interest in the book.

The beautiful thing about blurbs is that they can be changed easily and conveniently online. KWL has some useful tips on crafting book blurbs that will have more readers engaged in your novel and get those title sales up: