I thoroughly enjoyed this one, and the characters "felt" close to Sir Arthur Conan Doyle's original set.
I did not guess the whodunits, but the tale was as unexpected and convoluted as some of Conan Doyle's. It did not, however, follow S. S. Van Dine's rules for fair play for mystery writers to give readers a fair chance at solving it.
Even if Mark Latham's characters are close to the original set, there are a couple of discrepancies. Although today society often imagines a logical person more likely to be atheistic, in Conan Doyle's time that was not true. He wrote Sherlock Holmes to believe in God, particularly in accords with judgment in the hereafter. My favorite quote of his along the lines of belief is
"Our highest assurance of the goodness of Providence seems to me to rest in the flowers." - Sherlock Holmes in Sir Arthur Conan Doyle's "The Complete, Illustrated Sherlock Holmes."
However, in his later life, Sir Arthur Conan Doyle did become a spiritualist himself, seeking the spirits of the dead. Much of this book deals with those concepts, and the author, Mark Latham, does reference a book by Conan Doyle on the topic in his acknowledgments.
I'll agree with the reviewer that said Conan Doyle would probably have preferred Sherlock Holmes prove Spiritualism than disprove it. But I'll offer the clarification that in this story, ... SPOILER ... Holmes didn't actually disprove spiritualism in general, but disproved these particular spiritualists. There is a distinction.
But there's a key point here. Conan Doyle's views don't always have to agree with his character's views. Holmes was not intended as a character from which Conan Doyle wanted to launch his views into the world. Holmes was created for entertainment. I know from personal experience that authors can't always get their characters to behave, that if they are acting "in character," they are likely to be doing things that we'd really rather they didn't. At one point in time, I couldn't get a character of mine to quit arguing and actually do something. That took some maneuvering.
A second discrepancy between these characters as compared with the originals, Mark Latham's Sherlock Holmes said, "... the clumsy boots of well-meaning idiots." Conan Doyle's Sherlock Holmes certainly was arrogant, and spoke dismissively of other people, but he did not usually call them names. He may have called one person "a fool" at a moment of great crisis, but did not demean people while just calmly surveying a crime scene. He may have thought it, but he didn't say it, and since Watson is not an omniscient narrator, we don't know.
I am a little surprised to hear Mark Latham's Sherlock Holmes say, "One can think too much." I'm not convinced that Conan Doyle's Sherlock Holmes would've said such a thing, although I can't think of an example/counter-example to back that up.
I am not convinced one can think "too much," that is, if thought is making progress either towards unraveling a problem or in learning to cope with it. When people say they're "over-thinking," they generally don't mean that they are taking logical, reasonable steps towards resolution, though. Instead, they mean that their thoughts are running in unproductive circles. Instead of phrasing it as if one is thinking too much, I'd phrase it as one is not thinking effectively enough, or maybe not thinking enough at all. Perhaps it's feeling rather than thinking. It's the purposeful quality of the thoughts that are the question, not the quantity of them.
In this book, though, when Holmes said that Watson is "thinking too much," he meant that Watson shouldn't jump to conclusions. Holmes is being sarcastic. Watson had used the word "thinking," and Holmes sarcastically challenged him on it, saying, "One shouldn't think too much." He probably really meant that either Watson in particular shouldn't think too much, or that people, in general, shouldn't jump to conclusions and call it thinking.
Several reviewers complained that Sherlock Holmes didn't arrive until late in the book. That didn't bother me. I always preferred Watson anyway. He's more relatable.
Favorite quotes:
"I always find it remarkable just how the human mind can rationalize any misdeed if the cause is important enough." This quote makes me think of today's politics, where both sides are not above lies if they serve their political purposes.
"The facts, such as I could find, supported my hypothesis. But facts are a curious thing: when they are incomplete, they can lead even the best of us astray."
"I think we have given you false hope, when really, you needed help of a less esoteric kind."