Whether you are traditionally published or self-published, once your first book is out in public, you as the author have to commit a great deal of time to marketing it. This commitment can be exciting and exhilarating, but it can also be exhausting and time-consuming. You may be more comfortable wearing your writing cap than the marketing one, or you may find yourself putting so much time and energy into promoting your first book that you don’t have time left over for the second a course in miracles podcast. You need to find a healthy balance between writing and marketing, but you do need to write that second book.
The optimal time to write the second book is soon after you finish the first book. If you are going to publish your book traditionally, you’re going to have a lot of waiting time-waiting for agents or publishers to respond to your queries, and then, if your book is even accepted for publication, waiting roughly another year for it to be published. You probably have two years from when you finished the first book until you have to market it if you are traditionally published. Those two years you can spend working on the second book.
However, if you self-publish your book, you may be wise to wait to publish the first book until you have the second done, or at least a complete rough draft. Learning the ropes of book marketing is a tremendous learning curve that can consume all your time with that first book so be prepared by having the second book ready to go to print rather than trying to do marketing and writing at the same time.
Whether traditionally publishing or self-publishing your book, if you are writing a sequel or a series especially, you may not want to publish the first book until the others are written. One reason is so you can go back and make changes to the first book. You might decide while writing the last book of your trilogy that your main character needs a reason for a certain behavior, a reason stemming from something in her childhood. If you haven’t already published the first book, you can easily go back and revise to insert the details in book one to make book three stronger. Another reason to write your entire series before publishing it is that when readers realize you’re writing a sequel, they will anticipate the future books. You want to build momentum then by bringing out your books relatively close together, maybe a year apart at most. Authors who write sequels and publish books three or four years apart are likely to lose readers’ interests and sales. I know many authors who have had readers tell them they won’t read the first book until all three are published because they want to read them altogether, so the sooner you get that whole series published, the sooner you’ll be reaping the profits of your book sales.
For the second book, choose a topic that is different but similar to the first. If your first book was a fantasy novel with a quest, then the second novel might be a fantasy book but with a romance rather than a quest plot. If you wrote a historical novel, you might want to write a regular history book. If your first book was about overcoming fear, your second book might be about overcoming obstacles, or achieving your goals.
You want your second book to be different enough that people won’t feel it’s a rehash of the first book, but close enough that it will appeal to the audience that bought the first one. The differences allow also for cross-selling purposes. For example, a biography of President Theodore Roosevelt may lead readers to seek out your novel about Theodore Roosevelt, and vice-versa. If you are writing non-fiction, you might even work in references to your first book in the footnotes or main text. Without making it come off as a sales pitch, if you let readers know you have another book that may interest them, it is likely to sell two books for you.