This book gives an account of two celebrated theorems of Gelfand and Naimark for commutative C*-algebras, their tangled history, generalizations and applications, in a form accessible to mathematicians working in various applied fields, and also to students of pure and applied mathematics.

1. The Gelfand-Naimark Theorems: Historical Perspective 2. The Gelfand-Naimark Theorem for Commutative C*-Algebras 3. The Gelfand-Naimark Theorem: Arbitrary C*-Algebras 4. Banach *-Algebras: Generalities 5. *-Representations on a Hilbert Space: A Closer Look 6. Hermitian and Symmetric *-Algebras 7. A Further Weakening of the C*-Axioms 8. Geometrical Characterizations of C*-Algebras 9. Locally C*-Equivalent Algebras 10. Applications of the Characterization Theorems