In my younger days, I read Grace Livingston Hill's stories as often as I could find one I hadn't read.
Many authors have a formula of sorts that they follow. If you read several of their books in a row, you find that the stories are basically the same with different names for the main characters. That isn't true for Grace Livingston Hill. Each of her stories has a uniqueness about it.
This weekend, I found The Mystery of Mary in the new book section. I read it in about 2 1/2 hours. In spite of it being a short book and having been writing in the context of 1912, it is still a very readable story. It has stalkers, would-be kidnappers, an "escapee" from a mental institution, and a "knight in shining armor" type of hero.
If you liked Grace Livingston Hill in the past, this is your next good read. If you've never read any of her books, this is a fun one to start with. It is a gentle romance with an interesting plot.