Heller quotes Adam Michaels, the creator of the series,: ”Neglected by publishers in recent years, the mass-market paperback format remains highly desirable for its accessibility, both in terms of portability/usability and its low production and purchase costs.”
This and the recent news about the end of the Canadian publisher McClelland & Stewart made me think of the M&S mass market New Canadian Library series which began in January 1958 and ended in January 1978. A modified series began in 1981 and continues. Here are the first and last of the original NCL series.
NCL 1 - January 1958
NCL 1 back
NCL 152 - January 1978
NCL 152 back