Time for the nuts and bolts of book blurbs.
Step 1: Read the blurb content guide.
Step 2: Read the blurbs from your genre's top-selling books. How do you check which books are dominating your genre? Click on your categories on your listing.
Clicking on the bolded genre: Horror in either line of the "Best Sellers Rank" section will take you to the top 100 in that category.
Step 3: Utilize the Hero Line concept
What the hell is a hero line? Glad you asked. The hero line is the bolded line at the top of a blurb that establishes genre atmosphere—the most important part of the listing.
Firstly, to even make a line bold, you need to go into your Author Central page and click on the book's listing which will allow you to edit the details. You can edit the blurb there. Also, when you add spaces, the software will reject them. Go ahead and add them anyways, then message Amazon through the Author Central contact portal and tell them to add the spaces manually. Why / how a multi-billion dollar corporation like Amazon can't get basic HTML coding to properly display is one of the world's greatest mysteries.
What do you put in the hero line? Cool shit. Snappy lines. Atmosphere. More on that later (with examples!)
Step 4: Add some author bio
Toss a couple lines into the bottom of your blurb about you as an author. And make sure to cram a bunch of keywords into that section. Everything on the blurb factors into Amazon's search algorithms. Example: Bill Writerson, a 2010 Hugo Nominee for best upper thighs, crafts harrowing tales of epic fantasy, weaving all the suspense of a fast-paced thriller into worlds reminiscent of J. R. R. Tolkien, George R. R. Martin, and Dr. Suess.
See how many keywords we slapped down in just a few lines? Goal achieved.
Step 5: Talk about your other books
Why not add a couple lines below the author snippet to mention your other works?
Step 6: Drop a line about your website / newsletter
Yeah, do that.
Step 8: Wonder where step 7 got lost...
Nah, I'm out of steps.
Examples by genre:
Want to know the best blurbs in each genre? Me too. What I've assembled are examples I think are decent in each genre, probably not the best, but I'm not going to sift through 10 million books. Stop being greedy and do some research on your own.
Epic Fantasy: The Goblin Wars Omnibus
Dinosaur Erotica (you didn't think that was a real genre, did you?): Taken by the T-Rex
Sci-fi: The Martian
Romance: I Love You Again (this blurb is too long, but it uses the concept of the hero line quite well. Honestly, it has too much plot and not enough atmosphere)
Thriller / Urban Fantasy: The Victor McCain Collection (specifically, check out the last paragraph. That's how you drop keywords in an author bio snippet)
Postmodern sexual surrealism nightmare fuel (you didn't think that was a genre either? Buckle up.): Razor Wire Pubic Hair (check out the hero line and the author bio snippet—both are perfect, though I would have done them both in bold)
YA Romance: P.S. I Still Love You
Cookbooks: Thug Kitchen
Heavy Metal Cookbooks (by now you should believe every genre I throw out there): Mosh Potatoes
Non-fiction: The Space Barons