Spy fiction frustrates. Crowded with enthusiastic pretenders to the throne of Le Carre and Deighton, the genre rarely fulfils hopes for a genuinely rewarding plot coupled to uncliched characters (that is, spies who leap off the pages as real). All of this is preface to congratulating “The Insider” as a “classic” twisty Soviets-versus-Brits mole-in-the-middle adventure that weighs more than its plot. The author’s brilliant asset is Solomon Vine, a doughty, insomniac former spy recalled upon the murder of a London-based Russian oligarch who, known only to four top bureaucrats, had been a British asset. Can Vine track down the mole before national disaster? In framing the book’s central question as I have just done, I’m signaling that the plot is a fervid race against time from the Jason Bourne playbook, which would ordinarily turn a book cartoonish, but The Insider never feels less than solid, embodied in the figure of Vine, a natural spy gripped by love of intrigue. With a rollercoaster ending, The Insider snafu’d an evening of my life, and I can thoroughly recommend it.