Despite being political in content, the real nature of power and how it touches an individual is conspicuous by its absence in the novel.
In this sentence written by me, should I use the singular case?
Also, the is the use of "touch" grammatically correct and idiomatic here?
Yes and yes.
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There is a problem. You are saying that the nature of power is political in content. I suspect that you mean the novel is. I would recast the sentence.