Sentence:  McEwan certainly has a flair for unusual points of view. Adam, like the baby-in-waiting who narrates Nutshell, is an extraordinarily smart, well-informed, and unorthodox character who catches his supposed caretakers off-guard with his <WSD>perspicacity</WSD>. 
Meaning of the word marked with <WSD> tags:  Acute discernment or understanding; insight.