So I started listening to this podcast yesterday which is an interview with author & book coach Ella Barnard. I'm still only about halfway through the show, but there's a lot of good information about one of the paths to launch a book series.
As a book coach, she has her clients schedule a BookFunnel promo before they've written the novella. (This is a brilliant idea, especially if you are a procrastinator, but I can't even imagine doing so. Or rather, I may try this as a challenge at some point, but it's going to be a time when I'm on vacation from my day job.)
The idea, which seems to be the more or less accepted wisdom for indie authors, is to use the first book in the series as a freebie to encourage people to sign up for your newsletter. Then you have a newsletter of people who like to read the sort of thing you're writing, and you can send out notifications when something new is available. With any luck, a lot of those people will spend money on the next book.
I talked about Amazon ads a few days ago, and how you need to have about one person in ten who clicks on the ad actually buy the book (depending on the ad and book prices) to break even, but a newsletter is even better than that. Not only is it free (or almost free if your mailing list is very large) to send out an announcement of a new book, but that announcement is targeted specifically at the people who are your audience. None of the hassle of guessing appropriate keywords or categories on Amazon -- you already have a list of the exact people who are interested.
The bigger draw, in my opinion, is that you're no longer chained to Amazon, or at least not as tightly. I've read too many horror stories about Amazon removing books from their store and then not answering support email. If 95% of your author income stream is coming from Amazon, that might be a huge, house-foreclosing problem. But a newsletter allows you to advertise other places a book is available and partially removes that single point of failure.
I do have a cozy mystery novella that I was hoping to publish by the end of the month, but I think I'll hold off on the BookFunnel madness for a bit. I can always do the promo when I have the second one in the series ready, and that way I don't have to worry about having something ready on a specific date.