What term describes a book that summarizes the main points of another author's work?

The term that best describes a book that summarizes the main points of another author's work is "digest." A digest typically condenses the most important information from the original text into a more accessible format, allowing readers to grasp the core concepts without having to read the entire work. The creation of a digest serves as a way to present essential insights and highlights, often making it easier for people to understand and retain information.

While the terms "summary," "abstract," and "compendium" relate to similar concepts, they differ in context and usage. A summary typically refers to a concise restatement of the content but is generally shorter and may not represent the full scope of the original work. An abstract is often used in academic and scientific contexts to describe a brief overview that emphasizes the key points of a larger study, while a compendium is more of a collection of concise information or summaries on a related topic, without necessarily summarizing a single author's work. In contrast, the focus of a digest is specifically on summarizing another author's work, capturing the essence of the text comprehensively.