The phrase "large backlist" refers to a collection of previously published books by an author or a publisher that are still available for purchase. Full definition
I glanced at one point in the workshop at the thirty plus well - published writers, many with large backlists sitting in file cabinets, and realized there were at least thirty new publishing companies in that room. (deanwesleysmith.com)
Those figures match Beverley's 2013 results for authors with similarly large backlists. (jamigold.com)
On the plus side, I'm writing a series and saving up the books to publish close together so I have a large backlist, as Jami recommended. (lindacassidylewis.com)