There are eleven stories in this "grimoire"; stories where Holmes encounters crimes and/or events beyond the usual scope of the rational detective. Some are good, some are not. Many have little to do with classic Holmsian approaches.
The first story is "The Lost Boy". A combination of Holmes, Peter Pan, and a dash of H.P. Lovecraft. As a story it is "neither fish, nor fowl". It lacks the childishness of Peter Pan, the deductive trill of Holmes, and the terror of old HPL. The adventure is good, but Holmes attracting fairies?
Next is "His Last Arrow". This is a Watson driven story, and pretty good. But, again, the situation is not so much Sherlock Holmes as it is an alternate fantastic view of the detective. In other words, this is not a story about the great detective so much as a fantasy tale. It's still pretty good, and the ending is a surprise.
Now "The Things that Shall Come Upon Them" is a good story. With conflicting views as to weather there is a mechanistic vs. spiritual answer to the problem in on hold past the end of the story. Are they being haunted? Or are they being burgled? This one is good.
"The Finishing Stroke" is an inventive way to use the old "artist as mystic" trope. I liked it a great deal as a story. A pity the art at the start of the story kind of gave away the plot.
"Sherlock Holmes in the Lost World" isn't particularly good. A rehash of the "Lost World" dinosaur's plateau story with Holmes in it. Not much to recommend, either as a story or a Holmes pastiche.
Next is "The Grantchester Grimoire". I liked this one a lot. Again, the art at the start gave too much away, but it was a good, classic gothic tale, where the Detective was doing what we expect him to do. Missing evil books and ghosts at the windows lead to certain dark ends.
When I got to "The Steamship Friesland", I became a bit disgusted. This is not to do with deduction, but just having a ghost tell Holmes what was going on. Seriously, where's the Holmes connection, aside from the fact he's the one the ghost talks to?
"The Entwined" is a tough call. The girl confessing to murders she could not have possible done, but holding certain knowledge of them is a good plot line. The idea is good, but it's more HPL (as in you don't need a great deal of deductive ability) than it is Holmes.
"Merridew of Abominable Memory" takes place with Watson in a respite home, retelling a story of his former days with Holmes to the Doctor. Again, this is not so much a Sherlock Holmes story as it is a glimpse into horror. Holmes does play his usual role, but the point of the story is more about why Watson is hating his memories than the deductions of Holmes.
And then there's "Red Sunset". Holmes, at 100+, in a gangster 1940's situation. Need I say more? And there are vampires. And it's Dracula. And even with these spoilers, you couldn't appreciate the story less than if you read it cold.
The last, "The Red Planet League", is an interesting one. Holmes isn't in it. It's about a rather convoluted plan of Moriarty's (chronicled by Col. Moran) to get back at a fellow astronomer who has disputed his great book on asteroids. It's a good story, and a fantastic plot. It's a sort of anti-Holmes, showing all the meticulateness of a serious plan, just to be done for evil. I thought it rather clever, over all.
The collection as a whole disappointed, but some of the stories are certainly worth reading, if you can get them separate from the rest.