The idea is great, but it's not "in media res" which means "INTO the midst of things" not "IN the midst of things".
She might not have had Latin, so may not have known it
was a literary technique in Latin, and perhaps Greek, a way to start a story with no intro, just by jumping right into the action.
"INTO the midst of things" things could be very fitting as well, depending on your thoughts on the after life. Some choose to believe we join a party already in full swing...
This line is so beautifully & hauntingly crafted. I wish I had thought to add her books to my reading list sooner.