KenPruitt asks for books on stone efficiency. I am not sure if he really wants to know only about the efficiency of stones, and not about the efficiency of groups or global stone relations. So, at the moment, I assume that the question is only about the efficiency of stones, and that large scale considerations, such as directions, the shapes of groups or haengma, are not in the question's interest. Otherwise, more related books could be recommended. However, the efficiency of stones exists in a context of larger scale objects (groups, global relations), so reading books on the theory of directions, shapes or haengma helps, and there are such books, which can be identified easily by the keywords in their titles.

There is, IIRC, no English book discussing only efficiency or only efficiency analysis ("tewari"). Therefore, the following recommendations mention English books with significant discussion of theory about stone efficiency. The related strategic concepts and analysis tools are: efficiency, mobility, tewari, local positional judgement. There are these books discussing such theory:

- Joseki 2 Strategy: efficiency, mobility, tewari, local positional judgement.
- Fundamental Principles of Go: efficiency.
- The Vital Points of Go (old book): tewari.
- Joseki 3 Dictionary: efficiency (as implied by a method of joseki evaluation).