This classic textbook provides a modern and complete guide to the calculation of eigenvalues of matrices, written at an accessible level that presents in matrix notation the fundamental aspects of the spectral theory of linear operators in finite dimension. Unique features of this book are:* The convergence of eigensolvers serving as the basis of the notion of the gap between invariant subspaces.* Its coverage of the impact of the high nonnormality of the matrix on its eigenvalues.* The comprehensive nature of the material that moves beyond mathematical technicalities to the essential mean carried out by matrix eigenvalues.