Ostensibly a bestiary for Achtung! Cthulhu this is a little different because instead of, as in Call of Cthulhu, presenting the actual statistics of assorted Mythos deities - something no character is going to be able to withstand (they'll end up gibbering wrecks if not mashed to a pulp) - they've gone for an approach based on what they are likely to do and what might stave off the horror for at least a while.
Chapter 1: Dread Beginnings explains all this and more. If you've been reading/playing earlier Achtung! Cthulhu books, you might have noticed - particularly if you're a long-time Call of Cthulhu player - that most of the threats have been lesser, albeit nasty enough, manifestations of the Mythos not the real big guns. Now the gloves are off! A collection of real terrors is presented here, along with scenario ideas and a revised mass combat system designed with cinematic action in mind - and all dual-statted for Call of Cthulhu and Savage Worlds. Chapter 2: Death or Glory attends to the details of what is called the Simple Mass Combat System which will enable you to pit Mythos Terrors and their hordes of minions against hapless ranks of World War 2 soldiery, hopefully aided by some courageous Investigators who have done their research. Naturally rules for sanity loss are included, while the system itself is a simple turn based one where the Terror always acts last, performing one of the actions that it is capable of, as will be described in the next chapter. This chapter ends with an example of the combat system in practice. It really is quite straightforward, yet allows the characters to really have an effect.
The main part of the book is Chapter 3: The Faces of Terror. Here an array of some 24 Horrors (including Cthulhu himself) are presented in a standard format. This begins with a vivid description suitable for either reading alound when the Terror in question shows up or presenting (suitably edited and redacted) if the characters buckle down and do some research in advance. Next come some plot hooks suggesting ways in which you can engineer a face-to-face encounter with the Terror, followed by details of what will be effective against it (in most cases, causing it to retreat or otherwise come to the conclusion that easier pickings can be had elsewhere). Then comes the fun bits: the actions that the Terror can perform and how these are moderated in combat. If that Horror tends to hordes of minions, there's details of them as well.
If these are a shade too deadly for you, Chapter 4: Masters or Servants? offers some servitor races that can cause plenty of trouble but are not quite so overwhelming as the Horrors themselves. They do come with proper stat blocks, unlike the Horrors, and can be fought normally. Otherwise, each is presented in the same way as the Horrors.
Next, Chapter 5: Unconventional Weapons presents some 'weird science' contraptions that look almost as deadly to the wielder as they are to the target: try them out if you dare. Finally, Chapter 6: The Grimoire has a goodly collection of spells for those brave enough to learn and cast them.
The whole is presented in the standard 'bunch of papers out of a file' style complete with atmospheric pictures and marginal notes that makes it a feast for the eyes as well as the mind. The way of enabling you to bring the heavyweights of the Mythos right into the middle of combat without ensuring the total destruction of the entire party is really rather neat: all in all this is an excellent supplement for the game.