A yellow-back or yellowback is a cheap novel which was published in Britain in the second half of the 19th century. They were occasionally called "mustard-plaster" novels.^[1]

Developed in the 1840s to compete with the "penny dreadful", yellow-backs were marketed as entertaining reading. They had brightly coloured covers, often printed by chromoxylography, that were attractive to a new class of readers, thanks to the spread of education and rail travel.

Routledge was one of the first publishers to begin marketing yellow-backs by starting their "Railway Library" in 1848.^[2][3] The series included 1,277 titles, published over 50 years. These mainly consisted of stereotyped reprints of novels originally published as cloth editions. By the late 19th century, yellow-backs included sensational fiction, adventure stories, "educational" manuals, handbooks, and cheap biographies.^[4]

Two typical examples of authors of yellow-backs include James Grant and Robert Louis Stevenson.^[5]