In the present edition, a number of new features have been added. First of all, a number of typographical errors that had crept into the text have been corrected. More importantly, a number of new examples, figures and smaller sections have been added. In evaluating the two-body matrix elements which characterize the residual interaction, attention has been paid to the multipole expansion and insight into the importance of various multipoles is presented. The 18 example of 0 is now worked out for all the different angular momentum states in the section on configuration mixing. Some additional comments on how to determine one- and two-body matrix elements in jn configurations, on isospin and the application of isospin to the study of light odd-odd nuclei are included. In Chap. 3, a small section on the present use of large-scale shell model calculations and a section on experimental tests of how a nucleon actually moves inside the nucleus (using electromagnetic probing of nucleonic motion) has been added. In Chap. 4, some recent applications of the study of quadrupole motion in jn particle systems (with reference to the Po, Rn, Ra nuclei) are presented. In the discussion of magnetic dipole moments, the effects and importance of collective admixtures are pointed out and discussed. In Chap. 5, some small additions relating to the particle-hole conjugation and to the basic Hartree-Fock theory have been made. In Chap.