A trailer sells a feeling, not a summary
Nobody buys a book because a video explained it. They buy because thirty seconds gave them a feeling and left a question open. The trailer that works communicates one promise — this book will make you feel this, or answer that — and stops before the answer. Most book trailers do the opposite: they narrate the premise, introduce the characters or list the chapters, and by the time they finish the viewer has been given enough to feel finished. A trailer that satisfies curiosity has spent the only asset it had.
Thirty to sixty seconds, and no longer
Attention on autoplay video collapses fast, and whatever the trailer is going to accomplish happens in the first three seconds. Those three seconds decide whether the next fifty-seven are watched at all, which means the promise has to be legible almost immediately rather than built toward. A two-minute trailer is a two-minute trailer nobody reaches the end of, and the ending is usually where the author put the call to action.
It has to look like the book
A trailer built on different typography, different colour and a different mood than the cover is advertising a different product — and viewers notice the mismatch even when they cannot name it. This is why the visual identity has to exist before the trailer does: the trailer inherits it rather than inventing its own. When the cover, the site, the social cards and the trailer all draw on one system, each one makes the others more recognisable. When they do not, every asset starts from zero.
Cut for silence first
Most viewers see it muted, on a feed, while scrolling. If the trailer only works with sound, it does not work. That means text on screen, visible pacing, and a promise legible without audio — then sound added as an enhancement rather than a dependency. It also means captions, which are not an accessibility afterthought but the primary reading experience for the majority of the audience.
Where it actually gets used
The trailer is rarely the thing that converts on its own, and judging it by direct sales will always disappoint. It sits above the fold on the author website, on retailer pages where they are supported, in the media kit as proof that the project is seriously produced, in social ads where video reach exceeds static, and behind the launch announcement. It is an asset with many placements, not a campaign — and its value is cumulative across all of them.
What it costs, and what it substitutes for
A produced trailer is a real line item, commonly in the low thousands when commissioned separately — and considerably more when the producer has to start by reading the book and interviewing you to find the promise. That discovery work is the expensive part, not the editing. The reason it belongs inside the engagement is that the promise, the visual identity and the approved excerpts already exist. Built from canon, a trailer costs a fraction of what it costs built from scratch by someone meeting the book for the first time.