A First Course in Functional Analysis (Dover Books on Mathematics)

This introduction to functional analysis is based on the lecture notes of Martin Davis, a distinguished professor of mathematics. The treatment demonstrates the essential unity of mathematics without assuming more background than can be expected of advanced undergraduates and graduate students majoring in mathematics.
A self-contained exposition of Gelfand's proof of Wiener's theorem, this volume explores set theoretic preliminaries, normed linear spaces and algebras, functions on Banach spaces, homomorphisms on normed linear spaces, and analytic functions into a Banach space. Numerous problems appear throughout the book.

Martin Davis is Professor Emeritus of Mathematics at New York University. His other Dover books include Computability and Unsolvability; The Undecidable: Basic Papers on Undecidable Propositions, Unsolvable Problems and Computable Functions; and Applied Nonstandard Analysis.