Keeping the secrets: Tools of the Trade
The first is the Keeper Rulebook which gives important information needed to smoothly run the game. This is the book that you will find information on how to create investigators and the skills that are on the investigator character sheets. There is also the rules on combat, how to run a chase in game, or what is needed to successfully running magic in this crazy world. The Keeper rule book also has chapters on the Mythos and Necronomicon that rule the Eldritch horror realm that is Call of Cthulhu. Anything you need to be a successful Keeper can be found in this book.
Chapter 15 is also two scenarios that you can run your investigators through. If you could only get one thing, this would be the book that I would highly recommend.
The next thing that is important is the Investigators Guide. I have a copy that can be referenced by my players and myself at the table. I recommend that each of my players have a copy of their own to reference but in case it gets left at home I have the back up book.
The Investigator Handbook starts out as the basic manual of how to build a character and how to play, but there is a lot more to unpack in this 265 page manual. Because Call of Cthulhu is such a role play heavy game this handbook also has sections to help with life as an investigator by looking at things from the Roaring Twenties to truly bring your character to life.
An added gem is H.P. Lovecraft's classic story The Dunwich Horror is all of chapter two so you can read and get a feel for the master's writing and true style of the Cthulhu Mythos.
Why do I love my screen? Because it has so much important rules right at my finger tips that makes it easy to reference. There is a great chart to references for combat with arrows that shows all the options to help make sure that combat is done correctly and smoothly. There is the chart to help with firearms and other damages that investigators can deal/be hit with. There is a gauge for extreme difficulty that goes the entire length of the board. Need to roll for a bout of madness? The Keeper Screen has you covered.
My Keeper Binder
In my Cthulhu green binder I keep a few different things. First, I keep a blank character sheet. This way I have something to make copies of if a player needs a new sheet, and also I can have a quick look at this to see what investigator skills there are if I need a player to roll something.
I also have a plastic sheets that have common rules regarding skill checks, sanity and combat. Many of these things can be found on the Keeper screen or Keeper handbook but it is nice to have a quick reference guide with some more detail without needing to take time to page through the handbook.
The Introductory Rules book from the starter box also lives in my binder. There is a lot of the basic rules, skill descriptions and tables in this 23 page book so if a player has a question I can hand it to them. I mostly use it for the quick reference chart for half and fifth values on its last page.
I also keep the Keeper References booklet that came with the Keeper Screen pack in my binder. This booklet comes with a quick reference guide for everything from sample poison, mythos tomes, and in depth weapons tables.
Lastly, any hand written notes I keep for the Scenario I am running goes into a tab in my binder so I don't loose any of the prep work, or reminders I have written to make the game my own/ more interesting.