This book presents an unusual take on an campaign. Its core is a series of mysterious documents which the characters will be tasked to investigate; but the resources provided are very open-ended, chiefly people, organisations and locations with which the characters can interact. The course of events (apart from the actual appearance of the documents) is left up to the Keeper and to the characters themselves. This of course fits nicely into the investigative style of play so ably facilitiated by the Gumshoe game mechanic... but this book is even more innovative than that.
For it is left to the Keeper to determine the meaning of the clues in the documents, to decide which are genuine references to Mythos activity and which are something else - confusion in the author's mind, strange events of other than Mythos origin, red herrings, whatever. This confers tremendous flexibility on the campaign, but also relies heavily on the Keeper not just deciding what is taking place but driving events so as to keep the game exciting and on track. While a daunting prospect, the book goes a long way towards supporting the Keeper with advice on dealing with problems and using the ideas advanced by the players to weave a campaign that will be memorable for all participants. There is a lot of advice on running free-form campaigns which is useful whatever you are running, and a separate chapter specificially on using the Gumshoe system to facilitate them. The key thing is: nothing is 'wrong' even if it is not quite what you originally intended. It is possible to go even further, and openly take ideas proferred by the players but many groups are happier in the belief that their GM knows the solution to the mystery - the GM, of course, may still be prepared to change it when players come up with good twists, but does not have to let on!
These preliminaries done, the next few chapters contain detailed listings of people (each with multiple options to enable you to use them as good guys or villains as you please), organisations (again with alternate write-ups to allow them to be forces for good or for evil), places (which can either be neutral or sinister as appropriate) and a collection of tomes. The places come with 'stock footage' descriptions, a concept introducted in Shadows Over Filmland, where the description is crafted stylistically to envoke the scene. The entries in each category have suggested links to each other, and to the documents as well. It empowers the Keeper to have a battery of resources to hand so wherever the characters wish to go or whatever they want to investigate, there's an appropriate person or place or organisation or book to use. Many will spawn your own ideas for subplots or elements of the main plot as you read through them.
The next section, Scenario Spines, provides some outlines demonstrating how the documents can be used to spawn a whole range of adventures based on what you have decided about them in advance and what the characters choose to do once presented with the document in question. To demonstrate the flexibility of the concept, three different 'spines' basen on the first document are given, as well as sample ones for other documents in the series.
Finally the documents themselves, presented both as facsimile and as transcripts. For convenience, they are also given as a separate full-colour file (complete with bloodstains) that can be downloaded from the Pelgrane Press website, and are included in the download for PDF purchases.
This is a bold and innovative campaign concept, which will require a lot of work on the part of the Keeper; and probably will work best when all participants are experienced role-players willing to think, cooperate and seek imaginative solutions. Well handled, this will prove one of the most memorable campaigns you've ever been involved with!