What level of sales does a publisher require to keep a book in print?
It used to be the case that publishers would aim to have no more than three year's supply of a book in their warehouse. When stock started to run low, the publisher looked at sales and determined if they could get a reasonable unit price on three year's worth of books--the fewer copies that you print, the higher the unit cost, because there are fixed set-up costs that must be spread out over the printing. I can only draw on my personal experience in trade publishing, where it used to be the case (say, ten years ago) that a reprint of a novel could work if it was as small as 1,000 to 1,500 copies, while four-color picture books required higher printings, perhaps of as many as 3,000 copies. So if a novel was selling at least 500 copies a year, or a picture book 1,000 copies a year, it had a good chance to stay in print.
But changes in tax laws and inventory management practices mean that the number is now higher, at least at the larger publishers. Publishers look at the Rate of Turn (or ROT) in their warehouses. If a book has a low ROT--meaning it doesn't move quickly out of the warehouse--they will want to remainder it so that the space it occupies can be taken by a book with a higher ROT. In practice, that can mean that a book has to sell out a printing in one year or so.
Where the cutoff is varies greatly. Some publishers, such as Charlesbridge, remain committed to keeping their books in print, and will still print three year's supply if necessary. They may not keep every book in print forever, but they don't have the hair trigger that others, particularly the larger companies, do. I've seen books get remaindered after only a year in print. You can try asking your editor what the minimum sales are that you need to maintain, but they may not know. Decisions about reprinting a book or letting it go OP are often made by an inventory manager, perhaps with some consultation with the marketing department, but generally not with the editor.
What all this means to you is that if your royalty statements tell you that your picture book is selling fewer than at least 1,000 copies per year, or your novel is selling fewer than 500 copies per year, you can assume that it's in danger of going out of print, at least at most publishers.
What can an author do to help ensure the necessary sales?
The two best long-term strategies I know of are school visits and a web site, perhaps pursued in tandem. When a book first comes out, there are other things you can do, such as local publicity, but I'm assuming that you are looking a few years down the road.
School visits, if set up properly, will sell books. If you do 20 school visits a year, and the schools buy an average of 50 books at each visit, then you have personally caused 1,000 copies to be sold.
A web site should be more than a page of information about a book. Use it to promote your school visits. Have activities. Have information tied to the content of your book. Even if it's a simple bedtime story, you can create original content related to it--perhaps a list of great bedtime books, an opinion piece about the value of reading at bedtime.... Make the site a place that people will find via search engines and links from other sites, if you can, by providing real information. Aaron Shepard is a master of this kind of web site. You want people who don't already know about you or your book to find the site, and then decide they need the book (or books), so think carefully about how to do that. At the same time, you want the site to be a resource for materials to support your school visits, and a source of more visits.
These seem to me to be the basic things you might want to do, but read the marketing chapters in my Idiot's Guide, and the marketing tips on Susan Raab's web site, for more information.
Is it worth the effort to spend time keeping a book in print?
This is the really difficult question to answer. Publishers often discourage their authors from working too hard at school visits, local publicity, and other efforts that can help sell copies of a book. The standard advice is to write the next one, because that's a better use of your time.
I don't think that it's that simple. What if you enjoy school visits and don't work well if you spend too much time at your desk? Then go to schools. What if you have a book that you care deeply about, a book that you believe is unlike anything else available? Then you might want to plan on a certain amount of time per month spent on promoting that book. Or what if you are shy and love writing? Then go write.
What you decide to do depends on you and on the book or books, and I think you just have to figure out for yourself what you want to do. I hope these thoughts help you to do that.
