how do you do book ciphering?

Answer 1

A book cipher is a cipher in which the key is the identity of a book or other piece of text. It is generally essential that both correspondents not only have the same book, but the same edition.

Traditionally book ciphers work by replacing words in the plaintext of a message with the location of words from a book. In this mode, book ciphers are more properly called codes.

This can have problems as if a word appears in the plaintext that doesn't appear in the book then it can't be encoded. An alternative approach which gets around this problem is to replace individual letters rather than words, in which case the book cipher is properly a cipher — specifically, a homophonic substitution cipher. However, if needed often, this has the side effect of creating a larger ciphertext (typically 4 to 6 digits being required to encipher each letter or syllable).