miniature book
Refers to a very small printed book, often collectible or decorative. The term is straightforward and widely understood.
He is proud of his collection of miniature books.
This miniature book fits in the palm of your hand.
Compound of 豆 (まめ, 'bean', here meaning 'miniature') and 本 (ほん, 'book'). The use of 豆 to mean 'small' is common in words like 豆電球 (まめでんきゅう, miniature light bulb).