The Speckled Band is very cleverly constructed in that the mystery is carefully presented, dissected and solved by Sherlock Holmes.The use of Watson as the narrator regaling us of the dramatic tale is an engaging technique. Each of the clues to the mystery is carefully unravelled: the dwindling estate, the strange modifications to the ladies’ bedrooms and the strange animals allowed to roam the property. There is also the clever use of the gypsies to divert the less seasoned investigator.
The story is also satisfying in that the villain is punished for his wicked deeds. It is certainly poetic justice that Dr Grimesby Roylott dies by his own hand, whilst attempting to put into practice the evil plot by which he killed one stepdaughter, and planned to despatch another.
His chin was cocked upward and his eyes were fixed in a dreadful, rigid stare at the corner of the ceiling. Round his brow he had a peculiar yellow band, with brownish speckles, which seemed to be bound tightly round his head.
To say that this is a perfect example of a murder mystery is really a matter of personal taste, but the fact that the story has endured since 1892 suggests that its construction and content is worthy of some merit.
You might personally consider this a perfect murder mystery, but it is not a perfect murder since the villian didn't get away with his crime. Even if the doctor was never tried and convicted, there is indeed poetic justice in the fact that he died from the snakebite intended for another. Plus, his villainy becomes known to the public, which of course means that his already doubtful reputation "dies," too.
The odd parts that don't quite fit in the story line are perhaps not out of place in that they add depth and character to a story line which would otherwise be banal. The doctor's familiarity with the band of gypsies, for example, sends the reading off on a red herring (false supposition of who the culprit is), thus adding to the effect of surprise at the end of the story. His strange menagerie of exotic jungle animals, however, gives the reader some clues to unravel the mystery before the end. Thus the reader is taken up in a sort of guessing game, playing along with Holmes, and is either surprised at the end or gratified to have guessed right.
One thing I found rather trite was that the doctor was stupid enough to try the same trick twice - that is, sending the poisonous snake through the ventilator to kill his daughters-in-law. Surely a man of such ruse and intelligence could have thought up another way more subtle to achieve his goals.