Love may not necessarily be lovelier the second time around, and Steve Vail may not be more intriguing in this, his second outing as an ex-FBI-agent-then-bricklayer-now-pseudo-FBI-agent.
The Bricklayer, Noah Boyd's slam-bang first novel, was relentlessly paced, with clever puzzles and funny dialogue for maximum entertainment. The pacing dips in this one -- how could it possibly equal the first book in surprise and whoopee? -- and Vail is a little more macho, or his macho-ness is more noticeable (not a good thing). But, yes, I still found enjoyable moments in Agent X.
Kate Bannon, dedicated and proper FBI agent, and Vail sparked a tail-end romance in the first book. This book begins with the sizzle having mostly suffocated under a heavy load of expectations. Bannon is by-the-book and Vail threw the book away a long time ago. The only thing that could possibly bring Vail out of his second "retirement" from the Bureau is if Kate's life were threatened ... and a super-brainy villain called "Calculus" threatened to out some American moles in the Russian apparatus. So, voila! Kate is threatened and Vail is the only one who can discover the identity of Calculus.
Don't take it too seriously. Don't look for holes in the logic. Accept it for what it is.