ABSTRACT
Approval plans and cooperative collection development, as topics in the library literature, are like two long parallel lines. They are long lines, because librarians have been writing about these topics for decades. And they are parallel, because the lines do not cross. This is odd, because the literature of approval plans, after an early debate about whether they would or should survive, has since the 1980s largely been an exploration of how to make what has become for libraries a successful and widespread practice, yet more successful and widespread.1
