Blurbs, for those of you who might not know, are the quotes you often see on book covers, praising the book in question, the author or previous books.
There is a lot of work that goes into getting not just blurbs but the right blurbs, It wouldn’t help much to have a Stephen King blurb on a guide to walking around Bristol, nor would a David Attenborough blurb help sell a queer time-travel space opera.
You want a blurb from someone relevant to the genre.
Here’s an example of what I mean, from the back cover of Sing, Unburied, Sing.

And I am lucky enough to have one from Richard Thomas.
Richard Thomas is known to many in the horror and thriller community. He has a great number of books and anthologies out, he writes for Litreactor, and teaches over at Storyville.
Richard Thomas is the award-winning author of seven books: three novels—Disintegration and Breaker (Penguin Random House Alibi), as well as Transubstantiate (Otherworld Publications); three short story collections—Staring into the Abyss (Kraken Press), Herniated Roots (Snubnose Press), and Tribulations (Cemetery Dance); and one novella in The Soul Standard (Dzanc Books).
WHITESANDS is out in September, and this Richard Thomas blurb will grace the book:

Richard Thomas is a fantastic writer and I am thrilled and honored and humbled that he was willing to blurb Whitesands.
If you are a book reviewer and want an Advance Reader’s copy for review, please send me an email and I will try to get you one soon. My email is johann (dot) thorsson (at sign) gmail.com