This textbook has developed from the experience of the authors in teaching the course
of SoHd State Physics to students in physics at the Universities of Pavia and Pisa.
The book is addressed to students at the graduate and advanced level, both oriented
toward theoretical and experimental activity. No particular prerequisite is required,
except for the ordinary working knowledge of wave mechanics. The degree of difficulty
increases somewhat as the book progresses; however, the contents develop always in
very gradual steps.