Start with index.html for the Table of Contents.
This repository is a mirror of http://dhspriory.org/thomas/, the complete works of St. Thomas Aquinas, mostly bilingual Latin-English. This repository also includes a Calibre-generated e-book, Opera Omnia - Aquinas, St. Thomas.epub.
For his complete works in Latin, see CorpusThomisticum.org. See also Thérèse Bonin's continually-updated bibliography of Aquinas in English.