{PDF} Methods of modern mathematical physics. Analysis of operators Michael Reed, Barry Simon

The book covers the theory about eigenvalues of Schrodinger operators. It is complete success in explaining clearly the basic concepts involved: perturbation theory (summability questions, fermi golden rule), min-max principle for discrete spectrum, Weyl theorem, HVZ theorem, the absence of singular continuous spectrum, ground state questions, periodic operators, semiclassic distribution of eigenvalues, compactness criteria.