There are more books than you could read in a hundred years, even if that’s all you ever did. In a way, books are a commodity.
The firehose-stream of new books, both independent and traditionally published, makes individual books even harder to distinguish. Your only hope of being found is to focus relentlessly on the 1% which makes your book unique.
I’m not suggesting that you find a way to convince people that your book is unlike anything which has ever come before. If you’ve written a murder mystery, your book is 99% like every murder mystery since Poe invented the genre. If your book is a historical romance, ditto.
Potential readers will want to know the 99% about your book which gives them a frame of reference. Mention it, briefly, but assume they know what that 99% says about your book.
What prompted you to write this book in the first place? Why did you decide the world needed one more young adult fantasy novel, one more romantic mystery, one more travel memoir? Non-fiction writers tend to write the book they couldn’t find anywhere else. Fiction writers all believe they have something new to say in the genre they love to read, and rightly so.
Think about to why you wrote the book. What was it about your subject, your characters, your concept, that made you excited to write it? Remind yourself why you believed your book would be special, why you believed it deserved to be written.
A major portion of what makes your book unique is the fact that you are unique. Take the uniqueness factor you’ve remembered about your book and wrap it in thick layers of your personality.
That’s your marketing message: what makes your book special and unique in a voice no other author can duplicate.