This edition consists of two parts. This is Part I and you can find Part II by going to ISBN 9780201363005. A bundle of both books is available at a special, discounted price; please see the listing for ISBN 9780138166489. For nearly three decades The LaTeX Companion has been the essential resource for anyone using LaTeX to create high-quality documents. Just like the earlier editions, this completely updated third edition is designed to serve as the stable core resource for users: covering all aspects of document production, from detailed micro-typography questions and macro-typography (heading design, lists, mathematics, tables, graphics, fonts, page-layout, etc.) to bibliography and index production. All chapters have been thoroughly revised and in many cases largely extended to describe new important functionality and features. More than 5,000 add-on packages have been analyzed in detail, out of which roughly 10% have been chosen for inclusion in The LaTeX Companion. All important aspects of these packages are described to provide the user once again with a satisfying one-stop-shop experience for the decade to come. Following the concept of the earlier versions, the new edition is full of novel tips and tricks for using LaTeX in both traditional and modern typesetting, and also shows you how to customize layout features to your own needs--from phrases and paragraphs to headings, lists, and pages. New to this edition: Inclusion of, or more details on, important new or changed large-scale packages, e.g., biblatex, fontspec, hyperref, mathtools, siunitx, tcolorbox, tikz, and unicode-math, to name just a few. Coverage of newer engine developments, e.g., the use of Unicode engines with LaTeX. Discussion of all vital changes to LaTeX itself, which is is undergoing a transformation to keep it relevant in the years to come. Examples are the new hook management system for LaTeX, the extended document command syntax, and the inclusion of the LaTeX3 programming layer into the LaTeX format. Inclusion of many new, useful (smaller) packages in all chapters--each offering additional functionality. Two new chapters devoted to the use of high-quality fonts for text and math (OpenType, TrueType, and Type 1), now available for use with LaTeX. They offer a comprehensive set of samples to choose from, compiled with the help of an expert font designer. Revised discussions of multi-lingual support by the authors of the babel system to typeset text from a wide range of languages and cultures. The chapter on bibliography generation now also covers the styles made available with biblatex and biber. More than 1,500 fully tested examples (an increase of 30%) that illustrate the text and solve typographical and technical problems--all ready to run! This volume (Part I) of the edition covers: An introduction to LaTeX and its history The structure of a LaTeX document Basic formatting tools (paragraph level) Basic formatting tools (larger structures) Page layout Tabular material Mastering floats Graphics generation and manipulation Font selection and encodings Part II contains chapters on: Text and symbol fonts • Higher mathematics • Fonts in formulas • Localization and multilingual documents • Index generation • Bibliography generation • Managing citations • Package documentation tools • LaTeX programming and troubleshooting problems In short, the two parts of The LaTeX Companion, Third Edition, cover all you need to know about LaTeX use in the twenty-first century, while also offering expertly curated discussions of the best add-on packages now available--over 500 are covered! The examples can be downloaded from https://ctan.org/pkg/tlc3-examples. Register your book for convenient access to downloads, updates, and/or corrections as they become available.