Smiley's People is John le Carré's ninth novel, and the third and final entry in his "Karla trilogy" (behind Tinker Tailor Soldier Spy and The Honourable Schoolboy). Published in 1979, it chronicles the end of British spy George Smiley's attempts to solve the Soviet spymaster Karla.
Karla was first introduced in Tinker Tailor Soldier Spy as the unseen Soviet agent running a mole within the British secret service. In that novel, Smiley divulges that he actually met and interrogated Karla once and unsuccessfully tried to convince him to defect and stay in Britain. In The Honourable Schoolboy, we learn some more about another operation Karla was running. Smiley's People concludes the story and provides more details about Karla's background and history.
Smiley's People does more to advance the Karla trilogy's plot than The Honourable Schoolboy, though by his own admission le Carré seemed a little too set on tying up loose ends and finishing this plot once and for all. It's still a worthy addition to the Smiley canon, and as the final novel in which Smiley has a major role, it's a fitting send-off. It just feels a bit clipped given the more meandering pace of The Honourable Schoolboy. I personally wish he'd followed through on his original plan to turn the Karla saga into a long series of books, but if le Carré himself didn't think he had enough ideas, I guess he knew best.
Many characters from Tinker Tailor Soldier Spy and The Honourable Schoolboy return in this novel, including Peter Guillam, Connie Sachs, Toby Esterhase and Oliver Lacon. One of the book's pivotal scenes includes a nod to The Spy Who Came In from the Cold.
Without getting into specifics that fall on the wrong side of the spoiler line, one of the novel's most interesting aspects is its parallel between Smiley and Karla's respective personalities and how they've changed since Tinker Tailor Soldier Spy.
The BBC adapated Smiley's People for television and radio, with Alec Guinness reprising his role as Smiley in the TV version. It's been rumoured that the book will also be adapted as a sequel to the 2011 film version of Tinker Tailor Soldier Spy. Certain adjustments might need to be made to the storyline to accommodate changes made to Tinker Tailor Soldier Spy for the 2011 movie (Guillam's personal life might need some more rewriting) but it should make a fine film.
Update, 2016: Gary Oldman says the film adaptation is in the works.