I'm slightly perplexed by this book. And maybe working my ideas into shape hear will help me come to a consensus.
I think the plot is the best place to start. Because I think it was fairly good, if limited by the page count. Seeing Death Guard plague ships attack tau worlds was lovely, because the tau having to find solutions vs disease, something the book established well that they had completely eradicated in a prior generation, was enjoyable. Watching Shadowsun try and plan around a pox walker infestation, later paying off with a creative solution to short out the zombies neural lock, was actually nice to see.
The sub conflict with the tau sphere that, to me, arbitrarily turned racist vs the auxillary races felt unresolved. Either I missed something, or it went unexplained why they did this. Serving it as a set up for Shadowsun taking an alien-Expendables crew onto a plague ship felt like it tried proving a point without a fully developed thesis. I really liked the execution of that mission and it hits the theme of "stronger together" well. It just felt like it didn't pay off due to ineffective set up. And we don't even see any reward or acknowledgement of the auxiliaries that survived, other than stating that they did. Couple negative points here.
Lastly, I simply do not like the ending. Or, at least 70% of it. The Death Guard ship not being defeated felt like a cool win moment for the villain faction present, but the ship not arriving through the wormhole because the TAU HAVE A gOD NOW. Or always did or was called into minor existence from concentrated prayers drawn attention to earlier or whatever. Point is, hugely confusing deus ex machina, even if the 30% I liked was the reveal of the tau having a god. Super cool idea, massive implications, ravenously want to learn more, still kinda ass-pully to me.
And then Shadowsun herself. There was a certain amount of work done to make her feel distinct from Farsight. I think the attempt to layer in that they also share a fair bit in common ultimately undermined the effort. Particularly when this book already hit a lot of the same notes as the Farsight books, Shadowsun felt like her identity as a character within the IP just wasn't cast well enough. And maybe that's just because she's one of many 40k characters that exist right where they need to in the universe and can't make too many ripples. Would make for better fiction if they did though ...
Lastly, holy hell do I continue to ravenously want nicassar models. The kroot always seem to come off well in fiction, and so do the nicassar. Give us psyker bears pls.
Overall, I didn't hate the book. Fairly worth the short read, but really didn't satisfy enough. Makes me wonder if a better version arrived at an editors desk, then this version hit the shelves.
Farsight is so beloved by tau fans, I wish this book did more to prop up Shadowsun in a similar height for more people. Because I think she's great, her skills and legitimate grit are on display. Unfortunately, also with a hint of plot armor as well. I could've done with another 100 pages to show her having fever dreams of nurgle, then one of the others recovering from the warfront turns into a pox walker after saying yes to nurgle in a dream. THAT would have supplied more of what I was looking for. Because then she's sick with more at stake than slightly nerfing her, but not really.