In terms of plot, this is not my favourite Sherlock Holmes novel. However in terms of “quotability”, some of the most memorable lines that are often repeated in various subsequent adaptations originate here.
Holmes begins this investigation after experiencing a period of boredom, and it is here where we are introduced to his recreational use of cocaine. This is explained simply as a way of providing a distraction for Holmes’ mind, which must be continually challenged at the highest level in order for him to even function on what we would consider a more “normal” level. In modern terms we may have diagnosed Sherlock Holmes as having a mild form of Autism or Asperger Syndrome; particularly with his intense focus on a single problem to the exclusion of all else, and his apparent inability to view a situation from another person’s perspective.
The case presented in this novel also introduces us to Miss Mary Morstan, and her relationship with Watson. The mystery is in fact fairly straight forwards, and Holmes has much of it figured out before long, but doesn’t reveal his insights until he has tracked down the supporting evidence.
It is the character development which is the highlight of this story; of all the main players, Holmes, Watson, and Mary Morstan.