Two topics in the forefront of superconductor research—superconductor-insulator transition in thin films and vortex tunneling in granular, bulk, and high temperature superconductors—have never before been given a unified and deductive treatment. This monograph and text provides a much-needed, comprehensive introduction to the theory of quantum fluctuations in inhomogenous superconducting materials. It be will be of great use to students and researchers in disciplines such as superconductivity, many-body systems, phase transitions, submicron physics, and surface science.