What makes a book blurb sell
Your blurb is sales copy, not a synopsis
A synopsis tells an editor everything that happens. A blurb has one job: get a browsing reader to click "Buy" or "Read for free." Think of it as marketing copy built around what your reader wants. In practice that means you leave out most of the plot. Readers need a person, a problem, the stakes and a question they want answered. Subplots, backstory and the twist stay in the book.
Hook them before "Read more"
On an Amazon product page, only the first few lines of your description are visible before the "Read more" link.
Your first line has to work on its own.
- Drop the inciting incident: the body in the fridge, the letter that changes everything.
- State the impossible situation: "She has seven days to prove she didn't do it."
- Lead with a voice-driven line that shows the book's tone right away. This works especially well in romance and YA.
This is why the generator's edge-of-the-seat variant puts the hook first. Many authors use that version's opening line even if they prefer the body of the descriptive one.
Match your genre's conventions
Readers recognise their genre by its signals, and a blurb that breaks them confuses the very people you want to reach. Study a handful of current bestsellers in your sub-genre and note what their blurbs have in common. That's the idea behind the tool's reference-book step.
Romance
Both leads, the reason they can't (or shouldn't) be together, the main tropes named or clearly implied, and a hint of the heat level.
Mystery and thriller
The crime, why the protagonist has to be the one to solve it, and a ticking clock.
Fantasy and sci-fi
One striking piece of the world, a clear personal goal, and stakes that grow from personal to world-sized. Hold back on invented terms.
Non-fiction
The reader's problem, the result your book promises, and why you can be trusted. Bullet points scan well here.
Keep it tight and scannable
Most fiction blurbs work best at roughly 150 to 250 words. Use short paragraphs and white space, and end on an open question or a promise.
Tip
If a variant runs long, the Shorter preset is usually quicker than cutting by hand.
Format for the store you're publishing on
KDP allows up to 4,000 characters in the description field, and that count includes the HTML tags. It supports tags such as <p>, <br>, <b>, <i>, <em>, lists and <h4>–<h6>. <h1>–<h3> are not supported (KDP Help). The Format for Amazon mode handles this so pasted text doesn't break on your product page.
Use your blurb as a metadata hub
Your description also tells retailer algorithms which shelf your book belongs on. A spy thriller blurb that naturally mentions espionage or the CIA, for example, gives Amazon clear clues about who the book is for. Use genre words where they fit naturally, never stuff them, and back them up with the right backend keywords and Amazon categories. If you aren't sure your concept fits what readers in your category expect, run it through Write to Market before you lock in your blurb.