You need to get people talking about your book for it to become a bestseller. There are steps for a bestseller. Advance reviews, ready to release on your Day One, help accomplish this. You can get reviews into the world before the book drops. Even if you're publishing yourself, this kind of coverage is within your reach.
You do this with an investment to turn your Earned Media (coverage of the book) into Paid Media by purchasing a review from Kirkus.
Some authors, and even a few publishers, don't believe in purchasing review coverage. Jane Friedman says she's unsure if reviews from the likes of Kirkus or Midwest Book Review make any difference to a book. Getting outside coverage from those sources, though, delivers something to plug into metadata and your sales copy at Amazon.
Your alternative to buying a review is to rely on good blurbs from fellow authors, or lean on a reader review from an advance team member. Romance author Pamela Kelley has multiple bestsellers and offers this list of what works she does to sell her books. She's got money for ads, the Paid Media of the four-media bedrock of discovery services. Consider if this is within your budget. Ads are a gamble, but they can pay off with a long enough run.)
"What helped me more than anything was consistently releasing books in one genre," Kelley told me. "That helped me to grow my audience from book to book.
A publisher helps authors achieve those bullet points. The career work always falls on the writer's shoulders. Kelley said she's done all of that marketing on her own, up to now.
Now that there's Kelley's list of steps for a bestseller for you consider, does the modest investment in Kirkus seem easier to manage?