Salient Features The book provides a comprehensive introduction to the fundamental concepts, mathematical formulation and mathemodology involved in the development of quantum theory. It traces the development of the concepts and the basic interpretative postulates and reconciles them with ordinary real-life experiences. The development of wave mechanics, scattering theory including Eikonal approximation to the scattering amplitude, inelastic and double scattering phenomena are discussed in detail. It includes Schrodinger's wave mechanical language, provides solutions to most of the problems dealing with quantum systems, and discusses 'propagators' and various pictures of time evolution. It introduces the abstract vector space charascterisation of the quantum systems and the 'Dirac notation' and includes a section on 'Tensor Operators' and the 'Winger Eckart theorem'. A large number of solved examples would be useful not only to graduate students but also to students involved in advanced research related to quantum theory with applications to elementary particles and solids.