Miniature book

A miniature book is a very small book, sized from .5 inches square to roughly 2 by 3 inches—no larger than 3 inches in height, width, or thickness.

These books became more popular in the last few decades of the 19th century because they were portable and easy to conceal. One could carry a vast number of books in a small case for when one travelled. Many are bound in fine Moroccan leather, gilt and contain excellent examples of woodcuts, etchings, and watermarks. More popular topics at that time were dictionaries, language translators, religious stories and readings, and, occasionally, tourist guides.

Subjects range from the Bible, encyclopedias, music, stories, rhymes, famous speeches, and the miniaturization of well-known books such as The Compleat Angler, The Art of War, and Sherlock Holmes stories. Many are now collectors' items, with prices ranging from a few hundred to many thousands of US dollars.

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Wikipedia