Summary generation functionality generates summaries (“content briefs”) with respect to topics from an existing topic graph that organizes a set of keywords into related groups over a set of electronic documents, such as web pages. Each content brief provides a summary of a corresponding topic from the topic graph. Content authors can consult the content brief for a given topic to gain insight into how to revise or draft a web page or other electronic document to improve its ranking in a search engine with respect to which the topic graph was generated.