The other answer to this question does a great job of describing the foundations of manipulation as a theme in Dorian Gray, illustrating how Lord Henry manipulates Dorian, who in turn manipulates many other people. However, Wilde also partakes in some subtle manipulations of his own, setting up his readers for one kind of story before abruptly changing his narrative into something altogether unexpected.
For one thing, the beginning of the novel positions Lord Henry as a main narrative focus, and indeed as a kind of villain. However, midway through the narrative, it's apparent that not only is Dorian taking center stage, but he has also eclipsed Lord Henry as the narrative's villainous center: where Lord Henry's manipulation of Dorian is certainly morally suspect, he never engages in criminal activity as Dorian does (for instance, Lord Henry never murders anyone).
Moreover, at the beginning of the narrative, Wilde sets up his readers for a relatively straightforward character study...
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