There are at least a million KDP authors, and at least 5 million ebooks on Amazon (including a whole lot of traditionally published ones). Let's start with the statistics. If 1000 KDP authors are doing very well, then that means 99.9% of them are not. So if your book isn't selling, you are definitely not alone.
The very successful KDP authors have several things in common. (There may be the odd exception, but it is very odd and exceptional.)
They write genre fiction, romance, SF, fantasy, mystery, thrillers and the like. Maybe erotica.
They have published lots and lots of books. Their books are full-length (at least 40,000 words). Erotica may be shorter.
Their books have great covers, great blurbs, and are very well edited.
They spend a great deal of time, effort, and yes money, advertising and promoting, everything from signing up for Bookbub promotions to FBing with fans.
And finally they have been visited by the Good Luck Fairies, who showered them with fairy dust. Notice this is entirely unpredictable.
This means that if you write a short non-fiction or poetry book with an okay cover, with sort-of okay grammar and spelling, and it's your only book, you unfortunately have your answer why your book isn't selling. It's not the kind of book Amazon readers are looking for. The best Good Luck Fairies in the world won't, I'm afraid, be able to make up for this.
"But I see some literary fiction and non-fiction among the best-selling ebooks on Amazon," you say. Yes, but if you look closely, you will see that it is almost invariably published by a traditional publisher who has put ads in major magazines, gotten interviews on national radio, had the book reviewed by NY Times, etc., all options not available to us indies.
Those very successful KDP authors were not very successful on Day 1. Everyone starts somewhere. So there's hope.
But the main reason to write a book and publish it on KDP is the sense of accomplishment. Some copies may indeed sell, you may earn enough to buy a cup of coffee or a dinner or even pay for a vacation. But that's all gravy. Stick with sense of accomplishment.
Edited to add:
Author Earnings Report (see them at authorearnings dot com) figures about 1100 indie authors are making over $50k a year from Amazon, ebooks, paperbacks, audiobooks all combined. I'd say that much money, roughly the median for US households, counts as "doing very well."
Edited by: cdalebrittain on Sep 4, 2016 3:15 PM
Edited to add;
If you turn to page 12 (yes) of this thread, you will find some excellent suggestions by C. Gold on how to improve your cover, description, Look Inside. Might even attract the good luck fairies!
Great post. Sadly, most newbies either won't read it, or won't believe it.
The harsh truth is, writing is one of the worse ways to try to make a living. It always has been. The only thing that's really "easier" now is the publishing side. Anybody can publish. But not everybody can sell.
With all the scammers and opportunists out there telling people it's simple and quick to make money "publishing on Kindle", it comes off as the latest gold rush scheme, and that's far from the truth.
I was interested to see if I could comment on your question, Steven, but without a link to your books it's hard to comment. Are you the Steven Morris who writes about serial killers, data systems or chocolate cake? The answer to that question would definitely assist me to make a comment!