Aimed at players - whether of Call of Cthulhu or Savage Worlds - this book contains a wealth of material to help them understand the alternate history of a World War 2 with added Cthulhu Mythos elements, and hence to play their characters more convincingly.
Chapter 1: Welcome to the Secret War sets out the basic premise, beginning with a timeline of events running from November 1918 to April 1945. Despite comments about Mythos involvement, this is straight history... the weird bits get mixed in later! After all, to begin with the characters probably know nothing about it.
Next, Chapter 2: Keep the Home Fires Burning looks at life on the 'home front' - as opposed to the battlefield - telling how the war affected those not actively involved in combat just as much as it did those in uniform. There's a lot here from working life to fashion and food, even popular music of the day. Again this is historically accurate without the merest taint of Mythos, just as is intended for the game: ordinary folk got through the war without hearing about such things (much as it was only after the war that many Nazi atrocities were revealed). Chapter 3: Home Sweet Home continues this theme with a timeline of events in civilian life. A few suggestions about the style of adventures you might have on the home front are included, but this book is really for players rather than game masters (although they too ought to read it, it does not duplicate the contents of the Keeper's Guide to the Secret War). It all goes towards putting your adventures into context, however.
With the Home Front adequately covered, what of those who took up arms? Chapter 4: In the Service of One's Country gives an overview of the armed forces, intelligence and auxillary services mainly from an Allied point of view, although the German military machine is also covered. (Indeed, the whole book assumes characters will be drawn from Allied countries.)
Now that the scene has been comprehensively set, Chapter 5: Your Country Needs You! delves into the game mechanics involved in creating a WW2 Investigator character. There's an overview of the different nationalities from which he might come and a review of civilian and military occupations. Skills, pay scales, everything that you need to know about various occupations are included... and there's even a section on how to introduce a modicum of Mythos knowledge even before play begins by creating a bit of backstory to explain it - and perhaps explain why it's YOU and not someone else who gets embroiled in the sort of missions that are the basis of gameplay in this setting. For those intending military characters there is a review of the process of character generation under Call of Cthulhu rules, which in the original cater well for having a military background but are less good if you want your character to be in service when play begins. There's even a (somewhat inaccurate) note on the decorations he might have received. It also covers the civilian who has just enlisted (or who will do so during the course of the game). Unless you have a much-loved character which the game master agrees, it's recommended that you use these rules in conjunction with your chosen ruleset to generate your Achtung! Cthulhu character, as they've been written with the era and setting in mind.
Getting down to nuts and bolts, Chapter 6: Getting Your Hands Dirty introduces and explains new skills appropriate to this game, with Call of Cthulhu mechanics. Fear not, Chapter 7: The Savage Practice of War covers similar material under the Savage Worlds ruleset, if that is your game of choice. Chapter 8: Tools of the Trade mainly concentrates on weapons, with a wealth of detail about the different ones popular with various nations and units, complete with statistics for both rulesets.
To wind up, Chapter 9: Quick Play Guide summarises everything you need to know to create and play your character under either ruleset, and Chapter 10: Suggested Resources covers books, films and more that will enable you to understand the period better and get into the right mood.
Overall, this is an excellent introduction to playing in the Achtung! Cthulhu setting and ought to be read by players and referees alike.
[5 of 5 Stars!]