Yellow-back
（重定向自Yellowback）
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.
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.