There has been much written lately about publishing's "discovery" problem. In a nutshell, readers are overwhelmed with options for what to read next and authors struggle to get their work in front of new readers. Implied in any discussion of this problem is that any new reader will become a lifelong supporter.
The "post-discovery" problem acknowledges that an author's job is not done once she has gotten her work in front of a new reader who has gratefully accepted it. Rather, this problem recognizes that there is still a challenge in retaining previous readers. This challenge stems from the fact that even enthusiastic supporters of an author won't always be made aware when that author has new work available.
So the post-discovery problem boils down to this: How can readers and authors stay connected after they've made a match? In other words, once a reader has discovered and enjoyed a book by a particular author, how does she keep informed when that author releases a new one?
I suspect that most authors don't pay much attention to the post-discovery problem because it feels much less difficult to solve than attracting readers in the first place and because they would like to believe that once a sale has been made that future sales are guaranteed. Much of the rest of this post talks about the challenges of post-discovery as part of one of the most common book purchasing scenarios: after a reader buys a book from Amazon.
In this scenario, both the author and the reader rely on Amazon to communicate with the reader when new work is available from an author. However, Amazon has many varied interests which impact the frequency and nature of communication with their customers and so their communications may not always be in the best interests of authors.
First, Amazon is a diverse retailer and any individual Amazon customer is likely to shop in multiple categories besides books. Each of these categories is managed separately within Amazon and they compete with each other for the right to market to any individual customer during any given week. Amazon uses complex algorithms to determine which promotions a customer will see on Amazon's website and in any emails that are sent to that customer. These algorithms are continuously evaluated against a set of core metrics and constantly updated to improve performance against specific goals. Two of Amazon's primary metrics are percentage increase in cross-shopping (i.e. encouraging customers to shop in new categories) and increase in gross margin dollars (i.e. encouraging purchase of more expensive items which usually provide greater gross margin dollars even if the margin percentage may be smaller). Both of these core metrics work against book promotions because almost all Amazon customers already shop for books and books tend to provide low gross margin dollars. Therefore, if the Amazon algorithm determines, for example, that a customer is likely to buy a new blender in the near future then she will be more likely to receive an email from the Kitchen department than one from the Books department promoting a new book by her favorite author.
Second, unless a reader writes a review or rates a book, Amazon doesn't really know whether the reader actually enjoyed the book. It is important to note that if a reader is using a Kindle app or device to read a book then Amazon has the capability to determine whether or not she has finished the book and Amazon can use that information as a proxy for whether she enjoyed it. However, finishing a book is not as strong of an indication of enjoying it as a rating or review. That's one of the main reasons why Amazon strongly encourages readers to review books after finishing them and it is safe to say that they will continue to find new ways to get that kind of feedback from readers about what they've read. Absent any information about a customer's enjoyment of a specific book, however, Amazon might be more likely to promote a different product to that customer rather than a new book by the same author.
Third, even if Amazon's algorithms decide to promote an author's new book to a previous reader, the author has very little control over what that promotion says and how it looks. Amazon may use some elements of a book's bibliographic information (e.g. cover image, description, etc.) but an author won't be able to, for example, experiment with different cover images and blurbs to see which resonates more with readers. An author also won't be able to control the timing of this promotion. Many authors are beginning to recognize the importance of promoting books in advance of the publication date so that when the book is finally released it can ride a wave of pre-orders and release day purchases to a high position on the sales chart which will help drive even more sales. It is important, therefore, to increase awareness of new releases (especially among an author's most loyal supporters) well in advance of a book's release so that they can help an author spread the word about the new work.
If an author's audience is comprised of two major constituents (new readers and previous readers) then an author's marketing budget, in terms of both time and money, should also be divided in two ways: attracting new readers and reconnecting with previous ones. Achieving longterm success as an author is not just about increasing the number of readers in the first constituency (i.e. solving the "discovery" problem) but rather success is measured in moving as many readers as possible into the second one. Increasing focus on relationships with readers post-discovery will help authors retain readers which they've fought so hard to attract in the first place.