midlist

[mid-list]
noun
  1. the part of a publisher's sales list of newly or recently published books consisting of titles that are expected to have average sales or success, as compared to the frontlist.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for mid-list

mid-list

noun
    1. a section of a publisher's list containing those books that are not bestsellers
    2. (as modifier)a mid-list writer See also backlist, front list
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012