Book excerpt: Introduces a new method and language, based on finite topological spaces, for investigating molecular structure. Eschews the ``theorem-proof-remarks'' format of mathematics in favor of a more readable style commonly used in physical science. Part I develops the mathematical machinery which can serve as an analytical tool to investigate nonmetric aspects of chemical structure. Specific topics covered include set theory, lattices, graph theory, connectivity, classification of spaces, combinatorics, and functions and continuity. Part II explains the application of the above concepts to molecular structure. Chapters cover the bond topology, the graph topology, duplex spaces, and the topology of chemical reactions. Eight appendixes cover ancillary topics.