A backlist is a list of older books available from a publisher, as opposed to titles newly published (sometimes called the frontlist).
Building a strong backlist has traditionally been seen as the way to produce a profitable publishing house, as the most expensive aspects of the publishing process have already been paid for and the only remaining expenses are reproduction costs. A strong backlist is also a form of The Long Tail in modern business plans.
"The backlist is the financial backbone of the book industry, accounting for 25 to 30 percent of the average publisher's sales," wrote The New York Times. "Current titles, known as the front list, are often a gamble: they can become best sellers, but they are much more likely to disappear in a flood of returns from bookstores. By contrast, backlist books usually have predicable sales and revenues."[1]
Record labels also have backlists of music titles they have published.