The introduction to the great detective Sherlock Holmes, Dr John Watson having had his health damaged in Afghanistan is looking for lodgings in London and is introduced by a friend to Holmes who is looking to share lodgings in Baker Street.
Sherlock Holmes has bent his life and education towards turning himself into the premier detective, he can tell you about different types of cigar ash but nothing about the solar system.
Watson can hardly credit Holmes's claims of what a first-class detective can do. But, when a note arrives from a Scotland Yard detective inviting Holmes to consult on a particularly mysterious murder, Watson soon finds himself carried along by Holmes, watching his new friend unravel the case.
The book is quite markedly divided into two halves and the beginning of the second part is all background information (establishing motive) which reads at first like a seperate book and loses the pace previously set.
Thankfully Watson's narration takes over and the case concludes with a great partnership born.