Using sentence diagraming, Grammar by Diagram explains how ten basic sentence patterns can be expanded into more complex sentences, and how verbals can provide further versatility. The third edition includes more exercises at the foundational level, and also more focus on how to arrange and combine sentences for maximum effect. This edition also includes a new initial chapter on "preliminaries" to define a few basic but overarching concepts and a separate chapter on pronouns.

The Grammar by Diagram Workbook provides practice exercises, including cumulative exercises with which students can check their progress at key points, a "final exam" to test knowledge of the entire text, a summary of concepts for each chapter, and a complete answer key.