@lynnmosher had some good ideas. I will say THIS: I'm including a snip below of my lifetime sales on all 30 of my books over time. The bump in 2019 is because of a short giveaway. The results in 2020-present are ALL because of low-level marketing on Amazon Ads. Amazon allows you to set up ads, and place 'bids' on each 'presentation' (your book image in a potential buyer's face while browsing or searching for something. These are the 'Sponsored Ads' that show up at the top of your Amazon browse results). You may get 1000 views and only ONE click. The recommended bid is .39, so if a click happens, you pay 39 cents. If they BUY from that click, you make a profit, hopefully, if you have set your price high enough to realize a profit yet low enough to prompt a buy.
My figures of sales are quite low, even with the ads, because I have a $$ cap each month of $25 across all books. The bad news is that with the cost per click (ALWAYS use a CPC not a CPM (cost per view)) but the good news is that with 10 clicks I almost ALWAYS get a buy. This about pays for the ads, so it's a break-even, I got readers out of this.
If your cover is AMAZING, your ad text is RIVETING, and your first couple pages sell the book, you might net 1 buy per 5 clicks. If your cover is garbage, your ad text dull, your first page boring or off-putting, you won't get any buys no matter how many clicks.
SO, I SUGGEST THE FOLLOWING:
1. Make sure your niche market book is set into the PROPER CATEGORIES on AMAZON or anywhere else you want to sell it.
2. MAKE sure your first page, introduction, elevator pitch, all grip the reader, whether it's a novel or a textbook, a devotional or a wake up non-fiction for the elect. You have a message, a story to tell, something important to say, give a reader that wants what you want a message from your gut, put some passion and fire in there.
3. Make sure your cover is professional looking. You can make one with Paint.NET or GIMP, which are free, but craft a cover YOU would want on a book you paid good money for. There are plenty of good free image sites out there, and some you can pay a low fee for, that license and protect you from copyright violation issues (if your book doesn't get much spread, it may never hit anyone's radar, but we want to avoid any appearance of evil, and you wouldn't want that to bite you by just doing a Google Image search. You can also use your OWN camera and take pictures around your neighborhood, park, etc, or get a friend to allow a few images of their family at dinner, in the park, etc. A pic you took is ALWAYS your property, if you have written permission from the people in it.
4. Join the Bryan Cohen Amazon Author 5-Day Ad Challenge Facebook group. When he has a free 5-day program, it helps you craft a decent ad verbiage, identify your niche categories (that go on your Amazon book setup page and ALSO on the ad categories), and walks you through setting up your first low cost ad. At the end of the first month, you may have spent 5-25 bucks but you SHOULD have sales to offset that.
I will leave you with the following, though - look at the image below. I hardly sold ANY books for YEARS before I started investing in advertising. It was a hard decision to make, but it isn't charged until there is activity, and if you produce a product people WANT, you SHOULD at least break even.
