There should be an online service to help people author or co-author books. The difference from Google Docs or Microsoft Word Online would be the editor. You may be thinking it’s too little of differentiation, not justifying the efforts; but it’s not (more on this below,) and the monetization opportunities are many;
Justification of the Formatting Change Need
Just like how Medium revolutionized blogging with its truly WYSIWYG (what-you-see-is-what-you-get) editor, this company would change the space with its own. As they write, the authors would see their words and sentences in the exact same shape and format it would appear once the book is published. This would propel them to write more and give them a clearer picture of the length of their final work (especially for the first-time writers, who are the natural first-targets of this application.)
I’m sure if Medium founders were not veteran entrepreneurs, and they went out seeking funding, they would be ridiculed. Medium’s WYSIWYG editor (and the Applaud feature, to some extent) is indeed incremental (as many investors would criticize,) but just like the baking soda in toothpaste[*] it is the key ingredient. For example, I write this blog entry on WordPress using Gutenberg, which is a copycat of Medium’s editor because WordPress was left with no choice but to copy.
There are a bunch of monetization opportunities for this idea. Monthly SaaS is a classic one, but I don’t think it suits well here. Most writers are starving artists, so you don’t want to charge them upfront, but give them opportunities to submit their book for review by big publishers easily, and charge a convenience fee for the work, maybe in the form of a small percentage of the royalties. Of course, to justify that, the service should appeal to the writers so much that they should feel you are their companion in every step of their way. You can establish this with a sense of community, a forum for the writers to converse, ask questions, and an active blog.
Besides, you may charge for professional services like editing, proofreading, feedback services, etc. only for those who are willing to pay for such things, which I’m sure is sizable at scale.
Reaching writers won’t be very hard. It’s a close-knit community, and they tend to follow each others’ footsteps. Words spread fast. So if it’s a good product that you’ve created, it will sell.
As a first step, you may target writer trade-shows like the ones that are organized by The Author’s Guild to get the word out. The rest should grow like a snowball.
All in all, with some extraordinary front-end skills, and patience to create a long-lasting business, this may become a lifetime business opportunity.
[*] as Nir Eyal’s book, Hooked teaches us — highly recommended