This book is part general history of spying in the Cold War (particularly in Berlin) and discussion of the popular culture associated with it. It's also a game to replicate personal spy stories - basically stories like Le Carre's.
The history part is very good. It's concise, and packed with interesting facts. As well as that, it follows neither an academic historical format nor that of a typical history aimed at laypeople. It's somewhere in between, but not on a direct line. Perhaps it's just that it seems to reflect Edwards' own research and discoveries (and his excitement while doing that).
The game is quite specific and closed. You tell the story of two spies in Berlin during the Cold War. Characters are pre-generated and included in the book. However, the personal history and role as a spy are separate. Character generation is basically picking one person and one spy sheet, and sticking them together.
The other element to character generation is one that I find somewhat out of my comfort zone. Every player is required to write down two 'trangressions' - morally wrong things that they or someone they know has done. The player for each of the two characters each pick one of these at random and this act becomes part of the character's history. This feels like it's getting into a kind of psychodrama that I have no real interest in exploring. On the other hand, these spy stories generally include flawed characters and this method seems well picked to have a plausible and relevant flaw included.
The other players, by the way, share the responsibility for playing all other characters in the game.
Play proceeds by building up scenes, each player taking turns to add elements. The scenes generally are about one or the other spy, but everyone gets a turn to add to them. When the scenes reach a flashpoint (that's the game term - essentially a critical conflict) then you go into a card game to resolve that. Each player has a particular card associated, and a certain number (based on the character) are laid out. Then you play a few rounds of a game that allows you to maneuver your cards around. This allows you to influence the order of narration (each player narrates as their cards are placed in the line) and how much authority you have (e.g. if you lay a card on another player's, they narrate one thing and then you add to that; only if you have two matching cards may you narrate a character's death; etc).
Play continues through building up scenes to flashpoints until a spy's friends and companions are all removed from play - then the character comes in from the cold, one way or another. Once both spy's stories are over, the game is finished.