Does a GM need only the Keeper Rulebook from Call of Cthulhu 7th edition?

Question

To start GMing* Call of Cthulhu 7th edition, would I need both the Keeper Rulebook and the Investigator Handbook, or just the previous?

(I did google and check out some reviews online, but they failed to make this entirely clear – or I failed to understand it. That's also possible. Maybe I picked the wrong reviews.)

*or is it "keepering"? :)

Answer 1

Experienced Keepers

The rules for play and for character creation are present in the Keeper's Guide, and it appears to be meant to be a stand-alone book for a Keeper who is already familiar with the game, and its common setting of the 1920s. If a Keeper were shifting to this edition from an earlier one, the Keeper's Guide would be sufficient.

New Keepers

Those new Keepers without a grounding in the game, its inspirational material, its setting and conceits, and/or who wish to be in tune with the advice given to new players and with the point of view fostered for play will need to consider getting, or having access to, both.

Players

Likewise, players will find all the information they need to create and ground characters in the 1920s setting if they obtain the Investigator's Handbook and will require nothing from the Keeper's Guide. If they later intend to run the game as well as play it, however, they will need both.

Quickstart

It should be noted that the system rules are available in a PDF Quickstart format from the usual sources as well as Chaosium, so they can be investigated prior to making a purchase.

The Table of Contents for the Keeper's Guide

1. Introduction

2. HP Lovecraft and the Cthulhu Mythos

3. Creating Investigators
4. Skills
5. Game System
6. Combat
7. Chases
8. Sanity
9. Magic
10. Playing the Game
11. Tomes of Eldritch Lore
12. Grimoire
13. Artifacts and Alien Devices
14. Monsters, Beasts, and Alien Gods
15. Scenarios (2)
16. Appendices

421 pages of content

The Table of Contents for the Investigator's Handbook

1. Introduction
2. The Dunwich Horror
3. Creating Investigators
4. Occupations
5. Skills
6. Investigator Organizations
7. Life as an Investigator
8. The Roaring Twenties
9. Advice for Players 10 Reference
10. Character Sheets

268 pages of content

Answer 2

All you need to play the game is in the Keeper's Guide. I've managed to run a successful campaign using just that. We started with one of the two very good premade adventures found inside and then went into homebrew.

The Investigator's Handbook gives more options for the players and provides setting material for the 1920's setting to help inspire both GMs and players during campaign and character creation. There's more occupations, as well as more information about each one, and a few optional skills for them. Aside from that you don't need the Investigator's book at all to play the game. You can play just fine using just the keeper book and screen, which with how complicated some of the rules are (particuarly combat) I strongly recommend.