Finished reading A Sundial in a Grave by Mary Gentle a couple days ago. This is a historical fantasy novel and was a fun read, I really enjoyed it. Full of adventure, intrigue, and plot twists, I became quite immersed into the story. Though using number theory to predict the future is a pivotal element in the story — and thus making it a fantasy story to many — I disagree given that predicting the future would have been (as it is now) part of the culture of the time. There are also incursions into Rosicrucianism — though these occur later in the novel.
But really the novel’s enjoyment, for me, comes from the characters. At its heart its a character story with Rochefort the spy and murderer, Dariole young master of rapier and dagger, and later characters including the stoic but often amusing Tanaka Saburo. These adventurers must survive conspiracy, betrayer and the manipulations of the powerful as they journey from France to England and then much further abroad.
If you like adventure — with or without your fantasy — and love great characters, A Sundial in a Grave is heartily recommended.