I have now finished the draft of a thriller, yet to be finally named. Like my previous non-fiction book, God's Triangle, it will be self published, or indie published, if you prefer. There was a time not long ago when any self published book was considered a vanity project. Often it was a vanity project, of course, but sometimes it was just a book that was intended for limited distribution.
Things has changed dramatically in recent years. If some established and reputable publisher were to make me an attractive offer, I would consider it. Meantime, my book will already be out in the wide world and on sale, rather than sitting in some publisher's in-tray for months on end. Also, the marketing and everything else about the book will remain totally under my control.
The growth of self-publishing has, inevitably, resulted in a lot of unreadable rubbish being inflicted on the market -- mostly because of authors who arrogantly believe their work to be beyond improvement. Consequently, they publish it without seeking the opinion of potential readers (known as beta readers), let alone allowing their words to be professionally proofed and edited. But that is rapidly changing, not least because of the encouragement and growing power of independent publishing groups such as the Independent Alliance of Authors. This organisation encourages its authors to produce writing of the highest quality by getting their books properly proofed and edited. Some poor books will still slip through the net, but let's face it, there is a lot of literary trash out there that has gone through the traditional vetting and publishing route.
For more on the subject of self-publishing, go to this London Guardian article.