CHAPTER 12: KEEPER'S LORE
This is an invaluable chapter, with plenty of advice to Keepers new and old. There's a list of Maxims, with points like "Charts for random encounters, wandering monsters, and similar things are the bane of Call of Cthulhu" and "Since guns kill in Call of Cthulhu, resist tendencies to turn the game into gunfights." A nice sidebar talks about how to build a scenario for the game, and how to link the scenarios together into a campaign. Advice is provided on using law enforcement, asylums, and building atmosphere. There's a two-page spread of alternate rules (Hypnosis as a Skill, a variant Dodge option, speeding up research into tomes and spells, etc.). The only part of this chapter I didn't find useful (though I'm sure others will) is on tournament play.
CHAPTER 13: CREATURES OF THE MYTHOS
This chapter is almost thirty pages of monster descriptions and statistics, and there's quite a range of things drawn from the Mythos like Mi-Go and Byakhee. I quite liked the quotations derived from Lovecraft's or other author's writings about the monsters involved. I think a Keeper would have to be quite subtle and thoughtful in how these Mythos monsters are introduced, so that they retain their aura of weirdness and mystery and don't come across like something from the D&D Monster Manual.
CHAPTER 14: ALIEN TECHNOLOGY
This chapter is just a few pages long, and is a good example of where I'm not sure if the "weird" fits well with the "horror". Here you have things like brain-transferral, earthquake machines, time-travel, lightning guns, etc. This incorporates a science-fiction element into a game that is (primarily) occult and supernatural-oriented, and the mixture may not work for all groups without seeming silly.
CHAPTER 15: DEITIES OF THE MYTHOS
There's a lot of these, everything from Cthulhu itself to more obscure, lesser deities from the works of writers other than Lovecraft. Many of these deities are just so cosmically (comically?)powerful it seems almost absurd to have statistics for them (Nyarlathotep, for example, does 10d6+10d6 damage with a claw attack; one of the investigators in my game has--and always will have--a maximum of 7 hit points). The description of the deities' various cults is probably more helpful in actual game play.
CHAPTER 16: BEASTS & MONSTERS
This chapter covers normal animals (rats, bats, bears) and non-Mythos monsters, such as vampires, zombies, wraiths, etc. This latter category could be useful to Keepers who want to play a supernatural game that doesn't have strong ties to the weird-horror elements of the Mythos. As an aside, I really like some of the little touches the designers put into the game: Black Rhinos, for example, have a 70% Skill in "Be Annoyed."
CHAPTER 17: PERSONALITIES
This short section has full statistics and brief bios of some major characters from Lovecraft's stories, such as the famous Dr. Armitage of Miskatonic University, Herbert West of Re-Animator, and Wizard Whately from The Dunwich Horror. Milage here may vary, depending on whether or not the Keeper plans to have his investigators relive or follow up on events from Lovecraft's writing.
CHAPTER 18: A MYTHOS GRIMOIRE
Spells. A whole lot of them. Many are about summoning, binding, and dismissing various Mythos creatures and deities, but there are some really interesting ones that bring to mind adventure hooks just reading about them. The names of many of the spells are rather boring, and the Keeper is encouraged to add flavour to them. The descriptions are nice, however, as they work in non-uniform ways and many require unique rituals to cast. This is great because the last thing a Keeper wants is for occult practices to become standardized and uniform.
CHAPTER 19: THE HAUNTING (Spoilers: Don't read unless you're the Keeper)
The first of four scenarios presented in the book. This one is quite a classic for the game, having been included in every edition since the beginning, and reading the forums one sees it's the first exposure many players have had to Call of Cthulhu. Basically, the investigators are asked by a landlord to investigate a haunted house that has driven out all of its previous tenants. In a secret room of the house, they encounter an undead wizard. I wasn't very impressed with this scenario the first time I read it, as there's not a lot of interesting things to discover in the house and the climax seems too "on the nose"--destroying a lich (the only way to succeed in the scenario) just doesn't have the ring of original, grotesque strangeness I associate with the Mythos. Rereading it, I see better now how the investigation aspects of the scenario would be a nice introduction for new players--though most of the information they can discover is not particularly helpful in dealing what's inside the house.
CHAPTER 20: THE EDGE OF DARKNESS (Spoilers: Don't read unless you're the Keeper)
This looks like a *great* scenario, with a climax that is sure to be memorable and thrilling. The investigators are called to the bedside of a dying man, who tells them that he and some friends were once responsible for summoning a dark entity into an old cabin in the woods. The entity is still there, and now that the old man is dying, someone has to step in to banish the entity. This entity ("The Lurker in the Attic") is presented in quite chilling fashion, and can't be destroyed through mere gun- or swordplay (and burning down the house just sets it free!). The investigators, if they are to have any hope to succeed, have to cooperate on chanting a complex and difficult spell, while all the while the Lurker tries to disrupt the ceremony through attacks both physical (zombies) and emotional (illusions of the investigator's relatives in dire need). Very well done, with a great hook and a great story.
CHAPTER 21: THE MADMAN (Spoilers: Don't read unless you're the Keeper)
This is an interesting adventure, one that breaks from the "haunted house" mode of the previous two. It's also the one that most directly involves the Cthulhu Mythos, as the major adversaries in the game are Mi-Go who are trying to summon a deity named Ithaqua. Most of the action takes place in and around a forested mountain area, and I imagine the Keeper could have a lot of fun with the atmosphere the story calls for (forest fires, strange sounds, mists, etc.).
CHAPTER 22: DEAD MAN STOMP (Spoilers: Don't read unless you're the Keeper)
This is an urban adventure that heavily involves jazz-age (and mob) culture and social conditions in the 1920s. Black-White relations are a major subtext to the story, which at heart involves a jazz trumpet that has the unfortunate ability to resurrect the dead as zombies. It's a very interesting, original story and something I'd like to run because it takes advantage of real-world history. There are a few places that are quite railroady (assassins who "always get away"), however, and I'm not positive investigators have sufficient motivation to follow it all the way through.
CHAPTER 23: UTILITIES
This is a collection of a lot of various things to help out a novice Keeper. There's a map and key to Arkham; equipment lists for the 1890s, 1920s, and modern era; a list of historical and fictional events by year; eight quick-play investigators; and several monster- and character sheets.
The book is in black and white, with (in my opinion) some great, moody artwork--both full page drawings and several small pieces to help break up the text. It weighs in at 320 pages and (unlike a surprising number of RPGs) has an index.
Call of Cthulhu is a very interesting system. The rules are a bit esoteric and eccentric in places, but this actually works for a game that's all about weirdness. Characters are very vulnerable (physically and mentally), but this is a real necessity if the horror is to come through in gameplay. The main drawback I can imagine is that some players may not feel the joy of achievement gained in other campaigns where characters can be "levelled up" and grow significantly more powerful over time.