Sherlock doesn’t learn things that he sees as irrelevant like the theory of the solar system.
Sherlock asks Watson very politely to share their faults with each other to see if they can live together.
Mr. Lestrade is described as rat faced in the book
The word “rache” is spelled in blood on the wall because it means “revenge” in German
The motive for the killer is revenge for the death of the girl he loved who was forced into marriage
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