One of the suggestions I have seen most posted in regards to promoting self published books, both eBooks and those in print, is to keep writing. The more books you have on your bookshelf (assuming they are good books of course!) the better off you are as a writer, and the better off the books themselves are. The theory is that multiple books help to sell each other, a reader may not necessarily pick up my first book first, but if they read the second one, it will make them (hopefully!) want to read the first, or any others that I have written.
This in fact, happened to me with one of my favorites authors. I happened to pick up a Tana French novel when I had earned a free book at our local book store. It was a pure stroke of luck! It was her second novel and upon reading the first paged I was hooked. Immediately upon finishing that book, I downloaded her first and by the time I was done with that one her third been released. I pre-ordered her fourth and am now anxiously awaiting the next book. It was a brilliant chain reaction that worked just as any author would hope it too. Ms. French's writing is fantastic, which it what truly makes the whole chain reaction possible, but it was fascinating not only to read how it theoretically happens, but to actually also experience it firsthand. It was, as a writer, an almost profound moment, the idea becoming real in my mind. This is a tremendous motivator on those days that I don't necessarily feel like writing. I love writing, it is a great passion of mine, but even the most ardent of passions has days it doesn't flow. The idea though that all of my work, each piece of writing, actually works together to market each other and support each other, carrying each other further along is inspiring and often offers that little push that gets the ball rolling and gets the words flowing. I can, already, see the effects of this theory in my own books as well. Sales of the first have greatly increased since the release of my second. Both books have since gone to print as well, which also serves to bolster sales a surprising amount, but more about that another time.
In addition, this flowing, intertwining relationship my books have challenges me to continually better my writing. It pushes me to stretch my writing, fix past mistakes, and explore new ideas that will keep readers interested and coming back for more. Although I am not writing a series, yet, each book is tied to the others, and thereby must be as spellbinding as those that surround it, if not more so. Each book swims in the back of my mind as I work on others, the words, the ideas, the texture all serving to shape the books that follow and hopefully intrigue the reader with every turn of the page.