There have been a ton of books written about breaking into publishing, which equates to selling that first book. There’s nothing magic about it. It comes down to hard work. You have to have a great cover, great writing and great editing. Then you need to tell the entire world that you exist and that your book will be the best thing they ever read–if they are willing to read it. Beyond having a great product, marketing comes down to one word: recognition. People need to recognize you as a viable writer, and your book as a potential item for their reading pleasure.
But what about the second book? Once you get that first book out there, how do you make sure they come back and read your second writing project? Whereas the first book is all about recognition, the second (and every one after it) is about expectation. Your reader expect a quality product. If you don’t meet their needs, they won’t be back.
In addition, they are expecting something specific based on genre. Romance readers expect romance, with specific elements included. The same goes for westerns, crime stories, and science fiction. That’s why genres were created in the first place: so that readers will get what they are looking for, and so that writers will know what to provide.
Writers who try to write crossover books (myself included) are shooting themselves in the foot for that very reason. Readers–and publishers, marketers and bookstore owners–don’t know how to classify the book. And if you don’t have a classification, you can’t sell to a specific audience. Tough road, guys.
Expectation. Readers read your first book, they like it (or don’t) and hopefully look for more. If a writer jumps to another genre (me again), readers are going to be lost. They won’t see you as reliable, dependable. You won’t meet their expectations.
And you won’t sell that second book.