Each chapter focuses on a specific decorative technique such as flounces, stripes, piping, topstitching, pintucks, applique, bands and bindings, pleats and tucks, ruching, or faggoting. The text in each chapter discusses topics like how to alter a basic pattern, fabrics to use, pitfalls to avoid, etc. There are also many sketches and illustrations that provide inspiration and ideas for using the technique. Historic drawings and photos are used throughout, showing how the techniques were used in the past.
As a companion book, I'll also recommend "Make It Your Own: Personalizing Patterns for Creative Design" by Lori Bottom and Ronda Chaney, which is out of print but available at online bookstores like Amazon. There were several listings there, starting at $0.15 (yes, that's fifteen cents!). Although the subject matter is the same as "Decorative Dressmaking," its approach is different with an emphasis on the various parts of a garment, such as collars, sleeves, and necklines.