From the back cover:
Blasphemous Knowledge, Forbidden Secrets, & Handy Information
New to Call of Cthulhu? A battle-scarred veteran of many campaigns? Here is essential guidance and background to help you host Call of Cthulhu games more easily and skillfully.
13 Suggestions for Keepers - Common sense and sly applications to improve your games.
Occult Books - More than 60 occult books and references summarized, often including titles of individual chapters.
Languages and Scripts - A quick guide to when languages and language forms existed.
Arcane Antiquities - More than 20 items and artifacts not gathered by the rule book, taken from stories and scenarios. Background, pertinent stats, mechanics.
Secret Cults - Antagonists, allies, and scholars who know too much for safety or sanity.
Forensic Medicine - the science and techniques of death investigation, past and present, in cogent detail
Alien Races, Mysterious Places - Two short chapters concerning special mysteries of the Mythos, from deep ones and voormis to Atlantis, Yuggoth, and beyond.
Skills, Expansions, New Skills - fresh discussion of skill applications, coverages, and how some skills relate. More than 80 skills.
Plus Good Cthulhu Hunting, An Alternate Resistance Table, Feverish Study, Law Enforcement Timeline, Circumstances of Death by State, Brainstorming, Books and Sanity: Alternate Rules, updated Investigator's Sheet, etc.
The chapters 'Forbidden Books', 'Secret Cults', 'Alien Races', and 'Mysterious Places' originally made up the Keeper's Compendium and appear here in corrected or revised form.