A colportage book is a book from the beginning of the art of printing, which was intended for the retail sale. Colportage books were usually forbidden.
The regular books usually carried the name of one or more stores where they could be obtained. The colportage books are usually illegal and their printer or publisher is untraceable. The distribution of these books was made by traveling sellers who tried to bring them to the mansions in houses and markets.
In essence, these books are usually about quackery or magic, such as the grimace. Because of the illegality and the way they were worn, they were usually printed in a very small format.
wiki
