The blurb on the back:

It's 1895 and deadly games are afoot in London. Against a backdrop of terrorist dynamitings, a humbled Holmes reluctantly accepts the aid of Oscar Wilde to unravel two tangled plots: the blackmail of an eminent Victorian with a name known all over the world, and the diabolical design of a demented nobleman to inflict 'Death! Or Worse!' upon Holmes himself.
Sherlock Holms and the Mysterious Friend of Oscar Wilde mingles melodrama and epigram, fact and fiction, as two men with so many differences in common pursue a hellish hound whose actions menace all of England.

opening lines:
Queer people sought help from Sherlock Holmes, but the queerest of all arrived one morning in the spring of 1895.

Well, you know the form by now - we can just tick off the boxes. Sherlock Holmes meets Oscar Wilde, there's a gay frisson between Holmes and Watson; Mrs Hudson and the Baker Street Irregulars turn up, but Mycroft and Moriarty don't.

Frankly, it could all have been better. Brown borrows liberally from the previously published words of both Holmes and Wilde, but fails to make them really sparkle. Part of the problem is that Holmes is portrayed in his most reactionary light - the Holmes of 'His Last Bow' rather than the Holmes of 'The Sign of Fear'. This is a Holmes who disapproves of Wilde with all the homophobic horror you'd expect from a Victorian patrician. And that's just not very interesting really, nor is it very Holmes.

In short, there's not much here you can't get elsewhere. And, given that we have the presence of the Divine Oscar, that's got to be a waste of an opportunity.