From the Preface: The finite element method is now widely used in many areas of applied mathematics, physics and engineering....The object of this book is to give a thorough introduction to a number of theoretical fields connected with the finite element method....It has developed as a result of various lectures on the analysis of the finite element method taught by the author at the ETH in Zurich. Encouraged by the response to these lectures, the author feels that the book has become a readable text which can help ordinary mortals to start to understand the theory of finite element methods. The reader is assumed to have only an undergraduate background in mathematical analysis.