noun.
A small book or pamphlet containing poems, ballads, stories, or religious tracts.
The Century Dictionary and Cyclopedia
noun.
One of a class of tracts upon homely and miscellaneous subjects which at one time formed the chief popular literature of Great Britain and the American colonies.
the GNU version of the Collaborative International Dictionary of English
noun.
Any small book carried about for sale by chapmen or hawkers. Hence, any small book; a toy book.