Inseki refers to books in general on tenkoku (engraving letters on the material of a seal). It is also called insho or inbon.
Inseki can be classified into three categories: inpu (compilation of seal marks), inron (theory of seals), and story of engravers of tenkoku. The purpose of inpu is the study or artistic appreciation of inei (impression of a seal) and so on.
Inron can be further classified into theory of insho (seals), theory of tenkoku and theory of inseki. In Japan, a striking example is "A study of inseki", a unique inron, written by Soshii. Soshii wrote other books including "Compilation of Ingo (words engraved on the seal)" in which inmon (words or symbols engraved on the seal) and ingo are collected together.
As for story of engravers of tenkoku, major examples in China include "The Story of Engravers of Tenkoku" written by Ryoko SHU and "A Story of Engravers of Tenkoku, Continued" written by Keishuku OH, and major examples in Japan include "A Story of Japanese Engravers of Tenkoku", literary remains left by Keisho Nakai, and "A Story of Engravers of Tenkoku, Corpus" compiled by Chukei FUSHIMI.