This is the first of the Hugo nominees package I gave myself for my birthday; Neil Gaiman's "A Study in Emerald" has been nominated for Best Short Story and is the lead item in this anthology of authors attempting to meld the worlds of Sherlock Holmes and H.P. Lovecraft.
I've always had a liking for Holmes pastiches, and vividly remember as a teenager devouring John Dickson Carr's The Exploits of Sherlock Holmes, based around adventures mentioned but not fully recounted in the canonical stories, and Robert Lee Hall's Exit Sherlock Holmes in which both Holmes and Moriarty turn out to be time-travelling clones from the 24th century, but it's very well done as far as I remember. Also of course there's the early long-unpublished Bujold story, "The Adventure of the Lady on the Embankment".
And as for H.P. Lovecraft - indeed, some (all?) of the original stories are pastiche, most overtly the one where his friend and fellow author Clark Ashton Smith turns out to be the Whisperer in Darkness, Klarkash-Ton. And the tradition of Cthulhu pastiche has been alive and well for decades; an earlier Holmes/Elder Gods crossover which I much enjoyed was Roger Zelazny's A Night in the Lonesome October.
I'm sorry therefore to report that this is a pretty poor showing. Over and over the same themes get rewarmed - unspeakable entities in or from Afghanistan; the truth behind Colonel Moran and/or Irene Adler and/or (once or twice) Moriarty; dark hints, never fully explained, about bees. The editors have done a poor job with details of the setting - Guildford in Surrey has a "d", folks; Fylingdales in Yorkshire has no "r"; "Inswich" is a poor attempt to combine Innsmouth and Dunwich from Lovecraft with Bram Stoker's Whitby; the less said about the attempts at Welsh and Dutch the better (though I was amused to read the tale involving the young Princess Wilhelmina at Noordeinde Palace just two weeks after I helped celebrate her great-grandson's wedding there).
The jewel (the emerald?) of the collection is certainly the Gaiman story, which turns everything on its head to combine irony with horror. Three others, by Steve Perry, co-editor Michael Reaves and F. Gwynplaine McIntyre, deserve honorable mentions. But it would be better to leave the rest sleeping in R'lyeh with the Great Old One himself.