Having said that, I've picked up a few things, so I figured I'd share. If you're having a hard time with your book's blurb, then maybe this will help.
I like to write a three-part blurb, usually one paragraph per part. The first part introduces the main character and the "ordinary world" the character inhabits. The second part introduces the conflict and the "call to adventure." The final part states what the main character must do and what's at stake if he fails.
I also like to put a note at the end listing word count and parental guidance stuff, but that's an author's note, and not really part of the blurb. The blurb proper is an advertisement. It is meant to get the potential reader to click the "buy" button. Because it's an advertisement, the rules of marketing apply, not the rules of fiction writing. That means that cliches are acceptable in the blurb. It means that it's not only okay if your blurb is formulaic, but encouraged, because advertising formulas work. This is sort of a paradigm shift for fiction writers, and probably why so many of them get so frustrated with writing blurbs.
So let's write a sample blurb. We'll use Bram Stoker's Dracula. Here's the description of one version of the book on Amazon:
Dracula is an 1897 Gothic horror novel by Irish author Bram Stoker. Famous for introducing the character of the vampire Count Dracula, the novel tells the story of Dracula's attempt to move from Transylvania to England so he may find new blood and spread undead curse, and the battle between Dracula and a small group of men and women led by Professor Abraham Van Helsing. Dracula has been assigned to many literary genres including vampire literature, horror fiction, the gothic novel and invasion literature. The novel touches on themes such as the role of women in Victorian culture, sexual conventions, immigration, colonialism, and post-colonialism. Although Stoker did not invent the vampire, he defined its modern form, and the novel has spawned numerous theatrical, film and television interpretations.
This description is written this way because it assumes that everyone is familiar with Dracula. But let's assume that's not the case. Let's assume that Dracula is a completely new story that no one has ever heard of, and then write our blurb accordingly.
First part: introduce the character and the ordinary world.
Jonathan Harker is a young solicitor from Victorian England. He is engaged to Mina, a school mistress, and is eager to begin his life with her.
So far, so good, right? Moving on...
Second part: the conflict and the call to adventure.
His plans are interrupted when he is summoned to the Carpathian Mountains. He is asked to lend his services in support of a real estate transaction for Count Dracula. But things are not as they seem, and he quickly realizes he has been taken prisoner in Dracula's ancient castle. He manages to escape and return home, but the Count follows.
And now for the last part: what the hero must do, and what's at stake if he fails.
England is in peril, and Harker knows only he can expose the Count for who and what he truly is. With the aid of Professor Van Helsing and some friends, he pursues his elusive enemy. But he must hurry, because Dracula has plans of his own. If Harker fails to stop him, then all England will be enslaved to the Count's bloodthirsty will.
And there you have it. Not the best blurb in the world, perhaps, but sufficient, I think.
I hope that helps. If you decide to follow this formula, let me know how it works out for you.