TL;DR: The second Sherlockiana volume from Bonnie MacBird read a lot like the first one. It's an interesting story but not a terribly memorable one; if you enjoy full-length Holmes & Watson, this is a solid pick, though it's a bit gruesome and doesn't need to be nearly as long as it is.
Pro-tip: no need to read the first book before this one. MacBird has done us the favor, at least as far as I can tell, of writing stand-alone novels featuring SH&JW. There are references to things in the previous novel, but nothing that requires any prior knowledge.
What I Liked
I didn't guess the ending! I figured about Fiona, and Cameron's subterfuge + loyalty felt like it was resting on something deeper, but I didn't see the actual final twist coming, for once. That sounds a little self-important, but it's more frustration with how transparent so many thrillers can be.
What I Loved
How Holmes interacts with Calum, the groundskeeper's little boy. Watson particularly notes how his friend gets along with children in a way he can't with adults; he doesn't press the point, but it's a nod to the Irregulars, and it's a good example of MacBird's humanizing of the almost-real protagonist.
What I Disliked
Truly, this book could do with some editing. The hardcover edition runs to 492 pages, and although it was a good story and I did enjoy it, there's at least 50-75 pages in there that don't begin to pull their weight. The entire Jean Vidoqc / Dr Janvier subplot was absolutely pointless: it sort of served to give Mycroft a reason to finance Sherlock's jaunt to the South of France, but I forgot about it entirely during the bulk of the action in Scotland, and it doesn't move the action along at all. Jean's scene at the end is so jarringly juxtaposed as to be almost comical, like having Puck drop in unannounced on Hamlet.
What I Hated
Okay tho: the mash tun scene. What the fuck. I get that there was an existing malfunction, but just... no. I guess my suspension of disbelief refuses to allow for any artistic license on this one, but I run a brewery, and this is such bullshit, it was honestly difficult to read. Rest assured, if this scene ever presented itself in your real life, your ending would be very different.
You Should Read This if You Like
Sherlockiana, historical fiction, murder mysteries, slow-burn thrillers, overly descriptive scenes set in aging Highlands castles