As a child I though Holmes was a deductive genius and all-around hero. Not until I became older and learned more about the original character did I realize he was a jerk with a drug problem. This book puts those traits on full display, while also learning about the more reasonable and human sidekick/narrator Watson as well. 
 In addition to the characterizations, the plot is a success. Just as one mystery is solved, another mystery springs forth. There is never a dull moment. The boat chase scene is unequalled. 
 Quite compelling.