I just checked -- went down the list in Calibre of the most recently added books. Row 28 has "The Color Purple".
On the one hand, it's a "real world" fictional account with no supernatural elements. On the other hand, it's about a setting where a woman leaving her husband to live in an openly lesbian relationship with his former mistress in a small conservative community is completely accepted and no one really bats an eye.
So I would call that speculative. Hence my confusion.
But it's NOT A SERIES.