The game is newly afoot in 'The Sherlockian'

"anonymously sent letter bomb, which impels him to investigate a real mystery"

Though not incorrect, a curious use of the word impel when referring to opening a letter bomb.

Sounds like fun

Though the novel is packed with references to the vast Holmes canon, from the universally recognized “Elementary!” to more obscure academic tidbits, it is not at all necessary to have an encyclopedic knowledge of those stories.

Good idea, will look forward to the paperback.