Condon and Shortley has become the standard comprehensive work on the theory of atomic spectra. The first two chapters contain a brief historical introduction and an exposition of quantum mechanics along the lines formulated by Dirac. Then follow sixteen chapters devoted to a unified, logical deduction of the structure of the spectra of atoms from quantum mechanical principles. The theory is given in full detail and the results are amply documented with comparisons with experimental observations. When first published, a reviewer in Nature said that 'Its power and thoroughness leave the general impression of a work of the first rank, which successfully unifies the existing state of our knowledge, and will prove for many years a starting point for further researches and an inspiration to those who may undertake them'. Subsequent reviewers have amply confirmed these views. Science in 1952 commented that it 'has served half a generation and as a guide in further detailed research', and Reviews of Modern Physics in 1957 that this 'monumental book ...continues to be the most comprehensive account of our understanding of atomic spectra - the fruit of several decades' intensive study by a great number of physicists of all countries'.