1) Older titles, to a publisher 
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 ...
A generic term for books more than a year old, which are still available for sale.
Books published before the present year, but still in print.
Books from a previous year that are still in print.