"Referring to the moon" comes from an allusion of the Sixth Patriarch Huineng. Someone asked how to interpret the scriptures since Huineng was illiterate. Huineng replied that truth has nothing to do with words. Truth is like the bright moon, and words are the fingers pointing at the moon. Fingers are not the bright moon, only Buddha nature is where the bright moon is.
This book is a famous classic of Zen Buddhism. It has a total of thirty-two volumes and records the words and deeds of a total of 650 people from the past seven Buddhas to Zen Master Gao of the Song Dynasty.
A very, very nice book