Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
Third Person Omniscient
Doctorow gives us a God's eye view of the internal action within the characters. He zooms in and out of consciousnesses like a demented fighter pilot. We get an intimate look at Evelyn's take on her looks:
She had no joy. She looked into the mirror and saw the unmistakable lineaments of womanhood coming into her girlish face. Her long beautiful neck seemed to her like an ungainly stalk upon which was perched a sad-eyed ridiculous head of a whore past her prime. (11.6)
…And we get an equally intimate look at Father's aging:
He found he preferred to sit in the parlor, his feet near a small electric heater. Everyone in the family treated him like a convalescent. His son brought him beef tea. The boy had grown taller. [...] Father felt childlike beside him. (14.2)
This omniscience allows us to get a variety of different takes on the Ragtime Age and the stories that comprise Ragtime. It gives us a super-comprehensive look at not just individual opinions concerning the time period, but of the scope of the time period.
But keep in mind that the story of Ragtime is not being told during the period it's set in. The narrator has the benefit of knowing history, as we see in this quote:
And by that time the era of Ragtime had run out, with the heavy breath of the machine, as if history were no more than a tune on a player piano. (40.24)
Huh. The narrator knows how history unfolds during the 20th century, how long individual eras last, and how all sorts of events ended up shaping America. Really, the narrator ends up sounding a whole lot like a literary sort of dude in, say, the 1970s. Lookin' at you, Doctorow. We know your game.