"Strongly recommended" by the American Journal of Physics, this volume serves as a text for advanced undergraduates and graduate students of physics as well as a reference for professionals. Clear in its presentation and scrupulous in its attention to detail, the treatment originally appeared in a two-volume French edition. This convenient single-volume translation begins with formalism and its interpretation, starting with the origins of quantum theory and examinations of matter waves and the Schrödinger equation, one-dimensional quantized systems, the uncertainty relations, and the mathematical framework and physical content of formalism. The second half opens with an exploration of symmetries and invariance, including a consideration of angular momentum, identical particles and the Pauli exclusion principle, invariance and conservation laws, and time reversal. Methods of approximation include those involving stationary perturbations, the equation of motion, variational method, and collision theory. The final chapters review the elements of relativistic quantum mechanics, and each of the two volumes concludes with useful appendixes.