Many years ago, in the stone ages of print-only publishing, there were several nevers. Never write about a sports hero, an actor or a musician...the worst being country singers. Vampires were dead. (No pun intended.) Don't have anything supernatural in your book at all. Don't kill a dog. Don't mention God.
And don't even get me started about the "words" you weren't allowed to use. At. All. Ever.
Then pretty soon, the internet came along, and there was email, then Amazon, ereaders, epublishers, indie published writers and Konrath...and suddenly nothing was taboo. There are no sacred cows. There's no restriction on country singers. I'm reading a book about one now. LOL I've seen dogs killed and cats that talk. Witches and demons. Inspirationals and even, yes, Christian erotica.
If you want to write it...you can.
So the question becomes...should you?
The bottom line is money. (Drat.) Or maybe I should say the bottom line is your goal. Why are you writing this book?
If you want to change the world, have a story burning a hole in your heart, have a spouse who will pay the mortgage...you are free to move about the Internet.
If you want to earn a living, you're not going to have to pay attention to rules as much as you are going to have to watch what's selling.
Now, before you get angry and flick me off your screen...I'm not telling you to copy anyone's work. You could be the trailblazer who writes the next big thing. There are a lot of us who don't follow the crowd. I was actually laughed at when I wrote my first baby book. I've made a living out of those squirming, peeing suckers.
The trick is, your book has to be worthy of attention to become a trendsetter. If you're not first (and, trust me, just about everything's already been done on the Internet) then you have to be the best. You have to bring an insight to the table no one's ever brought. Or a tone. Or a plot. Or a character.
And, really, it's not that hard. (Stop throwing old shoes.) All you have to do is follow a few rules.
What? I thought you said there were no rules.
There will always be rules. LOL But, seriously, I'm not talking about no country stars or sports heroes or demon daycare workers. I'm talking about rules of great writing. There really are rules about what makes a great book. They differ from genre to genre in some cases, but it's very easy to find a how-to book on basic structure.
And, yeah, like Picasso, you might be the author who bends the rules until they break, and become a grand success. But Picasso also said, "You can't break the rules until you know them." (And have perfected their use or some such thing...Can't remember the quote verbatim.)
So where am I going will all this?
I believe there is a market for every book. :) You can write crap (or I can write crap) and put it on the Internet and somebody will buy it. Maybe lots of somebodies.
But if you want to be great, if you want your books to be loved, to be remembered...you need to take your time, learn the rules of your genre, and write a great book.
PS I looked up the Picasso quote...“Learn the rules like a pro, so you can break them like an artist.”