I tend to cringe when an author appropriates a famous literary character. It's not a fair response, since often the author takes the character into new and interesting territory. I guess my cringe is partly possessive. The famous fictional character belongs to all of us and I wonder what the new author is going to do to him or her.
However, none of my reservations can apply to Laurie King's brilliant pairing of Sherlock Holmes with her character, young Mary Russell. King remakes Holmes, but respectfully, breathing modern life into his sombreness while retaining his romance.
Because the Holmes and Russell novels are romances in the old sense of the word; tales of chivalry and adventure. O Jerusalem by Laurie King is my favourite. She brings alive the land of Palestine at the end of the First World War. I don't know its history well enough to judge historical accuracy, but the novel feels genuine and it powerfully conveys the passion of a land lived in for millenia.
O Jerusalem is a mystery novel, but it's more a novel of encounter--of landscape, relationships, identity and compassion. A pleasure to re-read.