Paul A. M. Dirac.
Principles of Quantum Mechanics: 4th edn.
OUP. 1958
The first edition of this work appeared in 1930,
and its originality won it immediate recognition as a classic of modern physical theory.
The fourth edition has been brought out to meet a continued demand.
Some improvements have been made,
the main one being the complete rewriting of the chapter on quantum electrodynamics,
to bring in electron-pair creation.
This makes it suitable as an introduction to recent works on quantum field theories.