"A poor Homes pastiche, despite the hype"
Almost everything.
All of the Conan Doyle characters are off, inconsistent with their characters in the original stories: Holmes, Watson, Lestrade, Mycroft, Moriarty, even Wiggins. Holmes especially does a number of rash, stupid things, and does little in the way of real investigation.
Plot-wise, there are two mysteries crammed together into one story here. The House of Silk mystery is fairly predictable, with an obvious clue dropped early in the story. The flat hat mystery, the lesser of the two, is more interesting and has a real flavor of the Conan Doyle short stories. The connection between the two is artificial and does not work well.
The framing story, that Watson is writing this old, long-suppressed story in a nursing home sometime after Holmes is found dead of old age on the Sussex Downs, borders on sacrilege for Holmes fans. The idea that the events in the story, especially a sensational murder trial in the middle of the book, were not well known publicly at the time is hard to swallow.
Overall, there is a definite Twenty-First Century sensibility throughout the story that does not fit Holmes's Victorian England. Horowitz tosses in a number of anachronistic phrases throughout the book, and flubs some of the details of the setting. The most glaring of these is Holmes lighting his cigarette on the gasogene, a device mentioned a couple of times by Conan Doyle and which has nothing to do with flame, heat, or anything else that might light a cigarette. Small things, but this is what the game's all about when you write or read a Holmes pastiche.
Jacobi is a fine reader, and I especially liked his reading of I, Claudius. He's not terrible here, but his portrayals of Holmes and Watson did not fit the characters well in my opinion. Of course, he's helped in this by Horowitz, who has them saying and doing things that are out of character for them.
Moriarty. His cameo appearance is senseless and out of character, his action is stupid, and his presence does not impact the plot at all. He seems to be there only because every mass media Holmes story these days includes him, unlike all but one of the Conan Doyle stories.
Also Watson's wife, who, like Moriarty, adds nothing to the plot. Both these characters intrude enough to slow the plot down, then vanish from the story.
It's not all bad. There are times when Horowitz does a good job of reproducing Conan Doyle's style. And the side issue that he raises about the Baker Street Irregulars is interesting. There is a reasonable progression through the story, and it moves along okay, except for a slow beginning where Watson unnecessarily retells the story of his meeting Holmes from A Study in Scarlet, and a couple other patches like that. This would be a decent story without Holmes and company, Unfortunately, as a Holmes story, it largely fails.
"a good, but un-Doyle-esque, Holmes story"
If (like me) you’re looking to read more Sherlock Holmes the way Conan Doyle wrote it, this book isn’t it. An aging Holmes shares the spotlight with the Russell character, who is his intellectual equal. This is her story, and it’s told from her point of view, not by a fawning Watson.
I’m one of those Homes purists who don’t want authors messing with the formula. I recently panned Anthony Horowitz’s The House of Silk for getting almost everything wrong, warping Holmes and Watson and most of the other Doyle characters beyond recognition. The Beekeeper’s Apprentice, despite its very non-canonical setup, gets almost everything right. The relationship between Holmes and Russell is believable while still being quirky in the way that Holmes himself is quirky, and I had no trouble accepting Holmes in retirement taking on the young Mary Russell as he does here. We get an outside view of Watson and his relationship with Holmes, and that also rings true.
If you’ve read all the original Holmes stories, this is an interesting take on Holmes’s later years that doesn’t conflict with canon or insult the intelligence. It’s a good book that is well worth reading--even if it isn’t more of the same old Holmes stories.
"Poirot at his best: short"
Poirot, like Sherlock Holmes, is at his best in short stories, and this is a collection of mostly clever ones. Agatha Christie has a tendency to cheat sometimes, and Poirot's deductions are sometimes little more than guesswork, but that's a lot more forgivable in a short story than a full-length novel. It happens in some of these stories, but they're good enough to survive it.
Also, David Suchet pretty much is the voice of Poirot now. He does it well here.
There is only one character that matters here.
"Ringworld wearing a Beanycopter"
Someone who hasn't read Ringworld. This is a slight variant on the Ringworld, and most of the interesting issues about the big artifact are the same ones dealt with, much better, in that book.
The aliens here are new, and it looks like there might be interesting issues with them, but the book ends in the middle of the story before any of that gets going.
If you haven't read Ringworld, listen to that book instead of this one.
Put a whole story into this book, or provided some kind of resolution or payoff at the end of it. Or at least labelled this as only part of a story, so I would have known to avoid it. This is not the first book in a trilogy, because it is not a complete book in any sense. It ends at a seemingly random, insignificant point in the plot.
Niven and Benford, individually, are much better than this. Listen to just about any other of their books, but skip this one.