Addresses several pivotal problems in spectral theory and nonlinear functional analysis in connection with the analysis of the structure set of zeroes of a general class of nonlinear operators. "The book is both an excellent introduction to some novel ideas about nonlinear eigenvalue problems and an exposition of a range of earlier results scattered in different papers and expounded in book form for the first time here."- Mathematical Reviews, Issue 2002"This is a nice introductory text about classical functional analysis?" This book will be interesting and useful for many mathematicians, scientists, graduate and undergraduate students."-Mathematical Reviews