From the inside flap:
"Vital films of Soviet troop movements in the Eastern Zone of Germany are lost and the courier killed. A small intelligence unit is authorized to put an agent over the frontier. . ."
This is a decent read. It has interesting characters, intradepartmental intrigue and edge-of-your-seat action, particularly when British agent (Fred Leiser) finds himself pursued by German troops on foreign soil, cut off from any support his agency (the Department) might offer him.
As an added treat for le Carré's regular readers, George Smiley and his boss, Control, get in on the spy-play, as well.
The element that mars this book is some of the transitional segments, where le Carré shows the workings of the agencies as Department agents, long out of the field, analyze their information and train Leiser for his secret border crossing; while some of the character chatter is necessary, these parts run a bit long - perhaps, as they might, in real life: to the novel's minor detriment, it sometimes bogs down the storyline.
So-so book, with some great characters and intriguing bits.
The resulting film, The Looking Glass War, was released in the UK in September 1969. It was released stateside on February 4, 1970.
Timothy West played Taylor. Ralph Richardson played LeClerc. Paul Rogers played Haldane. Ray McAnally played "Undersecretary of State". Anthony Hopkins played John Avery. Christopher Jones played Leiser.
Maxine Audley played Mrs. LeClerc. Anna Massey played "Avery's Wife". Pia Degermark played "The Girl".
Frank Pierson, billed as Frank R. Pierson, scripted and directed the film.