Since 2013 I've published one Civil War novel a year using Amazon's Create Space program, and their Kindle publishing program . I highly recommend Create Space. As others have described, the software is user-friendly and the cost is from zero to whatever you are willing to pay for extra editing, formatting, paper proof copies, and other services. I used Create Space's free cover options for Book #1, but have since used cover designer Karen Phillips for more "flash."
Those who point to the need for competent, if not professional, editing are on target. One of the fallacies of by-passing publishing house gatekeeping is loss of quality control. I choose not to pay a professional editor for what has become a compulsive hobby, but if I were writing novels or straight history books to pay the bills, then I would find a way to pay a proven copy editor. Among my worse moments have been finding typo errors in my finished novels--even after multiple volunteer readers, and my, and my wife's, own reading and rereading the manuscript, and the printed paperback proofs. Yet, those pesky little blips keep popping up, book after book.
The great thing about using Amazon's Create Space is that my Civil War novels are posted for sale on the world's largest bookstore right there with the big guns of Civil War historical fiction: Jeff Shaara and Ralph Peters, and others. That's been a huge ego boost to me personally. But, flipping the coin, with literally millions and millions of titles for sale on Amazon, it's easy for an unknown "wannabe" author to stay lost among the masses of titles.
We self-published writers have to market and promote our own books. Self-promotion is a built-in contradiction for most of us who are introverted enough to spend hundreds of hours by ourselves writing a book. Yet, we gotta do it and we have to be creative and persistent. For instance, see what my signature here includes? I also write an ongoing blog about writing and the Civil War and related stuff. I set up a table and sell my novels at Civil War reenactments.
All because, without almost ceaseless self-promotion, the stream of book sales becomes a trickle and the trickle can dry up quickly. So far, I only dream of a river of sales. But I know at least one self-published Civil War writer, Jeff Brooks, who has seen a river of sales for his excellent novel, Shattered Nation.
As to my success as an indicator of what one might expect: I write for the niche audience of readers of Civil War military fiction, and the unintended audience of my circle of friends and family. I've been surprised that as many women as men seem to read my books. The Amazon royalties are enough that I have to include the income on my IRS form, and I can take my wife out to dinner almost every month on my book sales. But I'm sure not buying a new car or going on a European vacation on the royalties.
Interestingly, at least to me, my Kindle sales are consistently more than my paperback sales on Amazon. Of course, Kindle downloads are a $3 or $4 per book cost to an Amazon customer, compared to a $15 paperback cost, plus shipping.
I hope this post will encourage other committed writers to jump into the self-publishing waters, but to do so with both eyes watching for rocks and alligators. While I've found a lot of personal gratification in self-publishing, the ego-crushing, pocketbook-crunching boogers are out there and the waters aren't clear.