1) In The Book Rache Is There Because It Is The German Word For Revenge
In A Study in Scarlet, the novel upon which the pilot episode is based, an official on the scene suggests that the message next to the victim’s body was meant to be “Rachel” and Sherlock Holmes corrects him, stating that Rache is actually the German word for revenge. In the episode the opposite happens.
2) Hamish Is The Leading Theory About Dr. Watson’s True Middle Name
The Scottish Doyle never stated what Dr. John H. Watson’s middle initial stood for. One clue is that in the books he is sometimes referred to as James. Hamish is the Scottish version of James.
3) Janine And Sherlock Holmes Both Retire To A Cottage In Sussex Downs
In Doyle’s short story His Last Bow we find that after Sherlock Holmes retires he goes to a cottage in Sussex Downs and spends his days beekeeping.
In the show Janine tells Sherlock that she’s going to take the money she got from selling stories about them to the tabloids, and buy a cottage in Sussex Downs. She mentions that “it has bee hives but…[she's] getting rid of those”.
4) Sherlock Can Never Remember Inspector Lestrade’s Real Name Because In The Books His First Name Is Never Revealed
We’re only told that his first name begins with the letter “G”. Every time Sherlock tries to call him by his first name on the show he uses a name beginning with “G”.
5) Janine Is The Maid Of Honour Because In The Books She’s A Maid
In both the books and the show Sherlock Holmes cultivates a romantic relationship with a member of Milverton/Magnussen’s staff in order to learn more about the villain. In the books it’s a maid and in the show it is the…maid of honour at Watson’s wedding.
6) Lestrade’s Theory About The Invisible Man Is Straight From The Books
Lestrade suggests it was a dwarf who was the Invisible Man in the episode titled The Sign of Three. In Doyle’s The Sign Of Four a dwarf is prominently featured.
Also note Louise Brealey, the actress who plays Molly Hooper, struggling to contain her laughter as Rupert Graves (Lestrade) delivers his line.
7) Northumberland Street Is In The Hound Of The Baskervilles
Northumberland Hotel was a real London hotel featured in Doyle’s novel, The Hound of the Baskervilles, located on Northumberland Street – the same place where Sherlock draws the killer in the show. These days it is home to the Sherlock Holmes Pub.
8) In The Books Sherlock Holmes Keeps His Pipe Tobacco In A Persian Slipper
Which is why in the show Sherlock is shown putting his cigarettes into a slipper.
9) The Stepfather Stepdaughter Due Are In The Books
In the episode The Empty Hearse Sherlock solves the case of a girl whose pen pal has disappeared. In the books as in the show Sherlock Holmes figures out that the pen pal is actually the step father, who was using a fake persona to keep tabs on his step daughter who is a source of funds for him.
A major difference is that in the show Sherlock seems ready to tell the duo that he’s solved the case, while in the books he controversially chooses to remain silent, afraid that he wouldn’t be believed.
10) Sherlock’s Protégé Is Inspired By The Books…Sort Of
In The Adventure of the Mazarin Stone we meet Billy who helps out the Holmes-Watson duo. And in the debut Sherlock Holmes novel, A Study in Scarlet, we meet Wiggins a boy who helps apprehend the killer. The name of Sherlock’s “protégé” on the show? Billy Wiggins.