I was at a writers' retreat in the mountains a few years back when a woman asked me to read the first few pages of her manuscript and tell her what I thought. I'm not easily shocked. At my age, I've been there, done that, heard that, seen that! However, those first few pages did indeed shock me. Just because you have an overwhelming urge to write porn or erotica, doesn't mean that someone else will pay to read it. If you write in this genre, the avenues leading to publication of your work are narrow, but with Google, I guess nothing is impossible.
Readers usually know what they want--romance, suspense, fantasy, true crime, action, the list is endless. When they go to a brick-and-mortar-book store, they head for their favorite section. And if they surf through online bookstores, they nearly always put a key word in a search engine.
Before embarking on your journey into the world of fiction, you need to know your specific genre and try to stay within those boundaries. "Joe Blow Best Selling Author" can get away with just about anything because he or she has name recognition. A newcomer doesn't. So, hold off on that time-traveling vampire cowboy. Make it easy for a prospective reader to find your book.
So...truly, it doesn't matter what your genre is (zombies, vampires, time travel, SciFi, shape-shifting, ghost stories or talking animals), lifting the veil of believability takes a delicate hand. Write your stories--but don’t slap your reader in the face. Stay true and don't wander.
Guide your reader, lead them gently by the hand. Make them a promise in the first few chapters and keep your promises or you'll have a disappointed reader. They want to care, want to worry and want a satisfying conclusion. If you give them a book with too many characters swimming in an outlandish plot, you won’t win any followers. Make them cry. Make them laugh. Make their hearts beat faster. Give ‘em what they want.