I ended up liking this (hence the three-stars) and don't want to sound overly critical here, because—again—I liked this, so maybe I'll say it a third time: I liked this.
Getting the world-building on the Fenris Rangers, getting some (fleeting) background on what happened to Voyager's crew since their return from the Delta Quadrant in the canon timeline (sigh, rest in peace, Splinter Timeline) was solid. I believed in a lot of what was put forth in the background as the idea of what it had been like for Seven since her return (especially that others wouldn't look past her ex-Borg status).
Now, some of Seven's early journey felt a little bit like it began from a set-back position—I kept feeling like she was re-learning things she'd already shown us she'd learned in Voyager, from an emotional point of view—but then, I'm willing to chalk up a great deal of that to masking; perhaps on Voyager it was more that she'd learned how to appear as someone the crew understood. Also, it was exactly that: a crew. The same people, day-in, day-out. Throw in suddenly being part of the Federation, and that's bound to knock someone off-kilter no matter how much she'd integrated into Voyager's smaller microcosm of a community.
The over-all arc of the story—Seven being offered something she wants, meeting the Fenris Rangers, getting in with them, coming to realize they're very much where she wants to be? Solid. The plot occurring throughout that—of heists and criminals and deplorable actions and the Federation turning its back on a whole sector because planets there have no official governments with which to call for aid? I struggled a bit with it in places—this is the Federation being the Federation and mucking things up, but it really read as kind of over-the-top in how much the Federation just... left, and then seemed to take zero care or responsibility about the mess they'd made, but at the same time, we've seen that with the Maquis, so it wasn't entirely off-brand, just frustrating as a reader.
And Seven of Nine being key to putting a major wrong at least to something slightly right and more just was an enjoyable journey.
Also, this was so casually, inclusively queer. Loved that for me.
So why only like?
Part of it was that "reset" feeling to Seven's awareness and understanding of human—and humanoid—actions. She seemed completely unaware of how evil individuals could be, but... this is Seven who encountered the Devore, fights-to-the-death in Tsunkatse, Species 8472, the Hirogen, the Equinox... She seemed to have no grasp of what a power-hungry dictator, or the desperate, might do if angered, and that seemed more than a step or two removed from what she'd encountered before. It felt like she got punished/forced to learn things when I struggled to believe she hadn't already known these things. So, a bit off.
The second thing is a frustration and limitation of the sub-genre of IP fiction. Introducing any new character beyond canon characters is an exercise in "well, this can't last." So, I was basically waiting for every death that happened to happen—a slight surprise in one character's non-death, though they don't get written out, either, they're just gone in the framing device of the novel that takes place years later—and so getting any sort of investment is next to impossible. It's unfortunate, but it aligns with the same way I felt watching Picard: Oh look, a guest character I loved from TNG. I bed they'll die—oop, there they go. It feels like the one play the narrator has to work with, but honestly at this point not killing these side-characters would be the truly surprising thing.
Lastly, and this is just a tonal thing for me and entirely a me-as-an-enjoyer-of-Trek thing, it landed very hopeless. One of my favourite things about Star Trek—indeed, the core thing for me—is how it's about the belief we can be better, and we're better when we work together, and the entire narrative framework of this book was instead hinged on the reveal of one of the most frustrating, hopeless things I disliked the most about Season One of Picard. While there's a victory for Seven of Nine in the plot throughout, the final scenes double-down by her noting how the Fenris Rangers are already devolving into little more than vigilantes without much in the way of actual justice and... sigh.
That aligns perfectly with where Seven of Nine is at the start of Picard, so I wasn't surprised, but it still left me finishing the audiobook with that slightly sour feeling overall. One of the things I love about Discovery and Strange New Worlds is the refreshing return of how competent and caring they are, and how it's about a Starfleet and Federation trying to be better, rather than individuals trying to do good surrounded by unrelenting "you'll never do enough."
But as I said, that's on me. There was nowhere else the book could have ended, really, given it's designed to do exactly what it did, and deliver us the Seven we meet coming to the rescue of La Sirena.