Sometimes, people ask me what it's like to write books. They want to know if it's difficult. The short answer is "no". Writing really is the easy part. Just step up to the keyboard and start logging hours—it's all about discipline. BUT the real time consuming efforts come after you've finished the draft of the manuscript. You send it to beta readers and review it yourself several times. Then, I suggest you engage the services of a professional editor. But do it with an open mind—you're going to see all the mistakes, inconsistencies, and other shortcomings you hoped weren't there. Based on that, you're going to spend considerable time rewriting (over and over again).
But wait! You're still not ready for prime time. If you hope to have any success in selling your opus magnum, you'll need to work on the marketing aspects. Done correctly, this will involve days— probably weeks—of research as you compile a virtual calendar of activities leading up to, and following, the actual publication of your book.
Sadly, despite all that time and effort and expense, there is no guarantee that your literary efforts will be recognized by a grateful world. But if you don't follow the steps described above, failure is guaranteed.