Difference equations appear as natural descriptions of observed evolution phenomena because most measurements of time evolving variables are discrete. They also appear in the applications of discretization methods for differential, integral and integro-differential equations. The application of the theory of difference equations is rapidly increasing to various fields, such as numerical analysis, control theory, finite mathematics, and computer sciences. This book is devoted to linear and nonlinear difference equations in a normed space. The main methodology presented in this book is based on a combined use of recent norm estimates for operator-valued functions with the following methods and results: - The freezing method - The Liapunov type equation - The method of majorants - The multiplicative representation of solutions - Deals systematically with difference equations in normed spaces - Considers new classes of equations that could not be studied in the frameworks of ordinary and partial difference equations - Develops the freezing method and presents recent results on Volterra discrete equations - Contains an approach based on the estimates for norms of operator functions