I believed it was originally supposed to be about Newt and his magical creatures. But JKR's politcal MACUSA seems to be the heart of the story. (jmo)
this page in wikipedia gives a whole lot of information about the story and the characters.
https://en.wikipedia.org/wiki/Fantastic_Beasts_and_Where_to_Find_Them_(film)one very interesting line in this page ... :
Fantastic Beasts and Where to Find Them is an upcoming British fantasy action film directed by David Yates and written by J. K. Rowling (in her screenwriting debut), based on Rowling's book of the same name. A spin-off and a prequel of the Harry Potter film series, the film will be the first installment of a trilogy, and stars Eddie Redmayne, Katherine Waterston, Dan Fogler, Alison Sudol, Colin Farrell, Carmen Ejogo, Samantha Morton, Ezra Miller, Ron Perlman and Jon Voight. Principal photography commenced on 17 August 2015, at Warner Bros. Studios, Leavesden.
it also goes to say that David Yates would direct at least the first installment (After Alfonso Cuarón declined involvement) ... ... Thank Goodness!! *phew* can't imagine how it would have turned out if nutcase Alfonso would have directed it. I guess (since it is Thanksgiving here) I have another thing to be extremely thankful for.