Thanks to BookBub for this handy little guide for pre-launch book promotion. There are some great insights, including why and how to get a blurb from another known author:
Secure blurbs from comparable authors.
Author blurbs can catch readers’ attention, especially if they’re familiar with the author providing the blurb. Our tests showed that book descriptions including blurbs got on average about 20% higher click-through rates than those without blurbs.