a nice writer person just emailed me and mentioned a blog written by Charlotte Rains Dixon examining the use of a type of plot structure she calls the "two nows." there are varieties within the variety. according to Dixon (if you scroll down the blog post), I used the thematic variety of the two-nows structure in my first novel, FORGIVE THE MOON. I guess I did, though I didn't know I was doing anything that had a name. I just wrote the book and then, yes, cut and pasted some chapters around to make psychological sense. (I created a bit of a mess doing it. at one point I had two characters sleeping together before they'd met. ) it's just what I thought of doing, partly because of my sense that time is layered, not linear, my trying to convey that.
in THE OPPOSITE SHORE, my second novel, I attempted to convey concurrent realities by alternating between the four points of view of the central characters, including two adult sisters, a husband and a teenager.
now, happily!, just yesterday I began reworking a novel I had set aside for quite some time. it also has two stories--a contemporary plot and a story set a hundred years in the past, partly in another country, the characters ancestors of the contemporary characters. so, this is something I guess I do.