I think this book tends to fill the bibliographic void left by the Classic and "currently dificult to get" works of C. Truesdell's "The Non-Linear Field Theories of Mechanics" and D. C. Leigh's "Nonlinear Continuum Mechanics; An Introduction to the Continuum Physics and Mathematical Theory of the Nonlinear Mechanical Behavior of Materials". This book is divided mainly in two parts, one part dealing with the mathematical framework at which the subject is based on, and the other one deals with the Physical Principles and the Constitutive Theories of several materials including rubber like materials and biological tissue. It is true that you will not find a specific definition of Nonlinear Material Behavior as I was supposed to find it at the begginig of the work. Instead of that, such a definition must be self-generated into the decided reader's mind, once he or she begins to read the book's parts regarding to Hyperelastic and Viscoelastic Materials .