Where is Whitehead going with The Underground Railroad?

It was 3 (not 4) chapters from the Underground Railroad that the NY Times published on Sunday; very intriguing start (I guess it was the start) of Colson Whitehead's novel - not entirely sure what to make of it but will most likely pick up a copy and continue. As noted yesterday, what starts out seeming to be a dramatic and reasonably realistic escaped-slave narrative takes some really weird twists and turns into the fantastic and the alternate history: the "railroad" that takes Cora and Cesar out of Georgia to a safer spot in S.C. turns out to be a real railroad line that sympathizers have dug and maintained - obviously an impossibility on every level - but we accept this as a signal that this will in no sense be a conventional narrative. And we see that right away, in ch. 2, as Cora is working as housemaid in S.C., a state that is in some ways much more progressive and sympathetic to escaped slaves, more than any other state - they're treated as citizens, with certain comforts and social advantages (housing, medical care, some protection) - but just as the bounty hunters were a menace in chapter 1 in Georgia, here the well-meaning sympathizers are a menace - conducting medical experiments on the unsuspecting black population, and trying to sterilize as many blacks as possible - and this part, ghastly as it seems, is probably not a fantasy but is based on fact. Cora, separated from her partner, head north once more in ch. 3 and finds herself on an abandoned spur of the "railroad," in N.C. - which, oddly, is a far more dangerous and reactionary state that SC or Georgia - she's moved north, but also backwards, and she lives in the cramped attic crawl space of a very nervous sympathizer (it's never explained in the least how these sympathizers can cover up such a massive movement of population). Core watches in horror the lynching of a black woman, the stirring of a gang of "night riders" - all this also based on fact, but pushed beyond the limits of naturalism, as N seems to be a world where black bodies hang from hundreds, thousands of trees. So, overall, not sure where White head is going w/ this or how it will develop - more fantasy and alternate history? or  but I may want to find out - though I think in some ways the true story of an escaped slave is about as powerful as a narrative can get (viz., the recent great film 12 Years a Slave).