Ironically, I've been talking about the relationship between lean publishing and serial fiction for a long time (for example, this video from a conference talk I did in 2013 - https://www.youtube.com/watch?v=ozO0kOnqmyA), but Leanpub has never hit anything close to product-market fit for fiction. We do well in our niche of computer programming / data science / business types of books, but we have essentially no traction in fiction for a number of reasons.
If an author was going to use Leanpub for fiction, the right thing to do would be to use our toolchain to generate the ebook and print-ready PDF, but then to also publish it on Amazon KDP and Wattpad for the exposure. For example, my teenage son did this with his debut sci-fi novel: he wrote it in Word (since he didn't want to write in Markdown, despite my best efforts to convince him that Markdown was superior), did a git push to his book repo on GitHub, generated the ebook on Leanpub (our Word support is an unofficial hidden feature; we just use pandoc to turn the .docx into Markdown first), and then uploaded it to Amazon. Ironically, the worst thing about this whole process was at the end: he also had to copy and paste the chapters into Wattpad when he did an update, and Wattpad wants small chapters for page views, so the copying and pasting was a very slow manual process...
My wife has toyed with the idea of writing romance novels. Do you have many romance writers on Leanpub? Her thinking is to keep the "trashiness" of most romance but improve on the story and writing. She keeps saying "I need a publisher", but I was thinking there must be a simple way to publish straight to Amazon, looks like that's Leanpub!
DIY publishing through Amazon is dead easy. Source: I once packed up my blog into a Word doc and had it published on Amazon in a couple of hours one night.
Naturally, I did it to win a bet. But the bet was designed to teach a friend of mine a lesson, that he was using the unknown difficulty of self-publishing as an excuse to not work on his book. He finally stopped procrastinating and finished his manuscript within a few months.
The hard part of selling books is the selling part. I similarly goaded my own wife into writing a series of sci-fi novels and we (pre-pandemic) had been going to book fairs to sell them. We maybe did two a year, mostly just for fun. We usually sell enough to cover our expenses (printing fees, booth fees, gas to travel, food while we're out). But along the way, she's earned a handful of loyal readers.
We've never put a lot of effort into it, but she sells a few hundred copies a year of her three books. It's not bad, especially for a vanity project. There is a clear line pointing from "effort in selling" to "books sold".
Most publishers these days won't even look at you unless you already have an active readership. We've met a lot of other authors at the book fairs, seeing the same people every year. The ones who have publishing deals are having to do all their own selling, just like us, but didn't get to choose their own cover and are giving up a huge chunk of cash to the publisher. For what? So they can say they're "published"? Meh.
I've seen a lot of people approach their projects as, "If you build it, they will come". I'm sorry, but that's just not a thing. The movie from which that quote comes from (Field of Dreams) is about a literal miracle. You have to sell the book. You have to get out and beat pavement, whether you get a publishing deal or not. So if you have to do the work, you might as well keep the money.
Regardless of what type of book your wife is writing, if she uses Leanpub she needs to do the upload to KDP herself: Leanpub doesn't currently do anything here.
There are other companies like BookBaby which do the "publish to Amazon for you" type of thing; Leanpub currently does not do that. We are just a toolchain to make ebooks plus an optional storefront to sell them. You can sell the ebooks you produce using Leanpub on any storefront such as KDP; you own your work. We do not have many romance writers on Leanpub, and a simple look at our homepage will explain why: our storefront looks like a place for computer programming books, not romance novels.
Also, most romance novels are written in Word, not Markdown, and our Word support is a hidden feature, kind of like the secret menu at In-N-Out burger. The way our Word support works is that you write in a Dropbox folder (or using GitHub or Bitbucket), and you make your Book.txt file list one or more Word files (instead of Markdown files) as the manuscript content. Then when you click the button to preview or publish the ebook, we generate the PDF, EPUB and MOBI based on those Word files, and you can do whatever you want with them. It's actually pretty smooth once you set it up, but it sounds really complicated, and we don't market it at all: hence another reason we don't have many romance writers on Leanpub!
Anyway, if that sounds like a useful thing then we may be worth a shot. Leanpub book landing pages look nice and professional, but in terms of attracting an audience of readers for a romance novel, we are not going to be much help. This is why places like Wattpad do well in this regard. (Leanpub does help attract an audience for our computer programming books and similar types of books, of course, primarily through our weekly and monthly sale newsletters.)
Frankly, my recommendation for any aspiring first-time novelist with a small social media following would be to publish in-progress on Wattpad first to see if they get traction, and then to consider Substack and Amazon KDP for places to monetize if they do. Then once they've gotten to that point, if they're looking for tools to produce a nice ebook to sell on KDP, Leanpub is one of the options they can use as a toolchain.
(On the other hand, if they have a reasonable social media following, they could skip Wattpad and go directly to Substack, KDP or even Leanpub and point their followers at the appropriate landing page for their book...)
There are smaller similar sites to wattpad that are easier to get viewers for new novels. I like tapas, but probably several more worth exploring (unsure if woopread is only translations or supports self publishing). I'd likely submit chapters to several sites at once as a new author just to increase chance of building an initial following.
Vanity Publishers (and variants like poetry "competitions") are a huge stain on the publishing industry. SFWA (Science Fiction Writers of America) maintains the Writer Beware website, a set of resources documenting, naming and publicizing such predators and their practices:
