of remainder and bargain (or discount)?
This site refers to "remainder and bargain book market", "bargain book trade", "bargain market". It also divides "discount books" or "bargain books" into four types - remainders, overstocks, promotional reprints and returns.
E.g.: The original idea of creating a trade fair specifically for the bargain and remainder book market ...
http://www.ciana.co.uk/FAQs.asp
See also this Frankfurt Book Fair document:
4.0 Modernes Antiquariat
Remainder and Discount Books
http://www.buchmesse.de/imperia/celum/documents/First Timer ...