Why God of Small Things is still a great novel

Continuing to (re)read novels that I at one time thought were great but haven't read in +10 years or so, I'm now about 1/3 of the way through Arundhati Roy's The God of Small Things (1997 - [corrected]) and I'm pleased to note that it holds up really well over time: It's as good as or even better than it was at first reading. Roy got lots of attention for this out-of-nowhere novel, her first, released first in India. Her career has been unusual to say the least; following up on this tremendously successful debut she shifted her work toward social/political activism and published a # of nonfiction book in that vein - none of which seemed to catch on with her world-wide readership - and she sort of fell off the literary map. She at lat published a second novel just a few years ago, and the reviews were tepid at best (I didn't read it). I have no idea where she's headed w/ her writing from this point on, but the achievement of God of Small Things is incontrovertible. (It's probably not read much today in part because Roy never built a career as a novelist - at least in part by her choice.) Like a # of the other novels I've been (re)reading, it's a history of a whole society - in this case the Syrian Christian sector of the southernmost Indian state of Kerala - through the vantage of a one family and one family business (a spice and pepper factory) - and we can see how this work is, at least in its theme, similar to, say, Buddenbrooks or Confessions of Zeno. The novel does get off to a rocky start, as Roy introduces many characters right at the top tells her story out of chronological sequence (which was a la mode in the 60s-80s in American and European fiction). But as we get more familiar w/ the characters - particularly in the chapters that involve a long family excursion to both see a movie int he nearest city (Sound of Music!) and then to pick up a cousin arriving for a visit (a visit that we know, from the earliest chapter, will end in her death) we see the themes begin to unfold and then coalesce: The tension between the "upper" caste and the so-called Untouchables, one of whom works in the family pepper factory and is politically active (and I think, if I recall correctly, will have a relationship with one of the daughters/cousins); the relationship between the brother/sister twins and the sexual abuse endured by the brother, Esthal, leading to his muteness and withdrawal from social interaction; the family generational squabbles and thwarted ambitions; the social upheaval in Kerala as the government cracks down on under-class activists. Roy's writing is observant, sometimes funny, often frightening (the abuse scene is terrible sad) - though her excessive use of sentence fragments makes the style sometimes a little too jaunty and stats; writing in complete sentences always makes a novel more "classic" and complete. What would Flaubert (or Proust) do?