The blurb on the back:

Here is another wonderful Sherlock Holmes pastiche from the prolific pen of Val Andrews. The author has a vast knowledge of conjuring and of Sherlockiana and in this exciting mystery he is able to combine both of his lifelong interests.
The Egyptian Hall, Maskelyne's theatre of mystery, forms the perfect backdrop for this the most exciting and unusual adventure ever embarked upon by the famous sleuth and his faithful Boswell, Dr Watson.
The loss of an article of great value - the property of a titled lady - by a conjuror during the course of a stage trick is but the prelude to intrigue, mystery and murder most foul. But hush we can say no more ... the game is afoot! Be sure that you are fully prepared for adventure before jumping into a hansom and returning to an age when the old Queen was still upon her throne and the fogs swirled through Baker Street.
Here is a real scorpion f a story with a sting in its tail to confound all concerned save Sherlock Holmes!

opening lines:
The year 1898 was a particularly busy and fruitful one for my friend, Mr Sherlock Holmes.

Val Andrews has made a habit out of writing Sherlockian pastiches (The Baker Street Dozen, The Circus of Fear, The Greyfriars Mystery, The Houdini Birthright and many, many more), and they're ... well, they're okay, you know. You can pass an hour and a half quite pleasantly, but there's none of the inspiration or insight that the best of these spin-offs achieve.

This one's set in the world of Victorian stage-conjuror and inventor JN Maskelyne and features his successor, David Devant, which is all perfectly agreeable, if unstartling. You probably didn't believe that claim on the sleeve that it was Holmes' 'most exciting and unusual adventure ever' and you'd have been right not to do so.

There are also a couple of annoying glitches: a mad German character is introduced, for example, who is clearly supposed to be Holmes in disguise, but who disappears and is never again referred to. As part of his eccentric behaviour, he leans out of a railway carriage window shouting 'Deuchland Uber Alles' - apart from the misspelling, 'Das Deustchlandlied' (as we call it) wasn't adopted as the German national anthem until 1922, and though it did exist, it's unlikely to have been used in this context at this time.