Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
Third Person (Objective)
This reflects the action-packed, plot-driven nature of the Three Musketeers. Although most of the action focuses on D’Artagnan, there are quite a few chapters that concern other characters.
While the narrator is omniscient in that s/he knows everyone’s backgrounds and personal histories, s/he never intrudes nor does s/he ever directly reveal characters’ thoughts and feelings. Luckily for us (and the purposes of the novel) we still get access to all the swashbuckling and nefarious things that they do.