SWEET TOOTH by Ian McEwan

The title gives the impression of a confection, but actually it refers to a fictional undercover operation during the 70s in which MI5 secretly funds 10 writers with anti-Communist leanings.  Serena Frome's job at MI5--up until Sweet Tooth comes along--has been basically clerical.  Her favorite pastime—reading fiction—has won her a role in Sweet Tooth, recruiting and mentoring an aspiring novelist named Tom Haley.  They fall in love, but Tom is in the dark about Serena's true occupation and the role of MI5 in sponsoring his work.  These secrets haunt Serena, as she attempts to convince herself that their relationship can thrive without her divulging these unpleasant facts.  The secondary characters actually have the juicier roles.  Serena's former married lover, now deceased, dumped her in a very hurtful manner, for reasons not revealed until later in the book.  Her lower-class friend and co-worker Shirley seems bent on sabotaging Serena's position at MI5.  Then there's Max, Serena's superior at MI5, on whom Serena has a crush before she meets Tom.  Max initially spurns Serena's advances because of his upcoming arranged marriage, but then he does an about-face, which has a disastrous impact on Serena's job and personal life.  In other words, most everyone has some sort of hidden agenda.  Certainly all of this intrigue has its appeal, even if national security is not at stake, but I was particularly entertained by Tom's short stories, which Serena summarizes for us during her vetting of Tom as a candidate for Sweet Tooth.  The one called "Pawnology" is my favorite, as it delivers a surprising and twisty punch.  Also, Serena provides a very enlightening explanation of the Monty Hall probability riddle.  Then Tom builds a story on it but misses a key aspect of the riddle.  Serena's rewrite and million-door analogy make the solution crystal clear.  She may have been a mediocre math student at Cambridge, but she grasps more than we give her credit for.  So does Tom for that matter.