Hello!
It isn’t, actually...I just love the name Isolde. I didn’t realize that my history of writing retellings + the name would lead to the assumption it was a Tristian and Isolde retelling, LMAO. My bad.
Anyway, it IS steeped in mythology and history, however. The monsters in the stories are all some type of vampire from various cultures across the world. I also reference many Romanian myths and the witch hunts were influenced by those lead by James I.
The only other book that isn’t an overt retelling is When Stars Come Out, which is my YA. It’s very loosely based on Orpheus and Eurydice but those themes aren’t obvious.
Hope this helps!