The difficult part of writing this review is going to be making sure that it's not longer than the source material. Field Report: Alien Races can't really be called a book. It's more like a pamphlet. It's roughly 20 pages of fiction about three of the game's alien species.
The most notable thing about this book is what's absent - any new information about the fourth alien species. The shadowy psionic entities, lurking in the background of the setting's major events, pulling strings and manipulating the psi orders for their own ends. I know they exist because I read the "Setting Secrets" section they added to the back of the 2nd printing core book. With that piece of information in mind, they are conspicuously absent from the descriptions of the species they were exploiting.
That's just how Trinity did things, though. Release a slow drip of information, from book to book, so that if you read all the supplements, in the order of their release, you'd get a dramatic build, as the full scope of the setting reveals itself, hidden agendas are revealed, and shocking events threaten to forever change the world you thought you knew.
It's mostly kind of a bummer. I don't have direct confirmation, because I never read the adventures, but I suspect this book serves mainly to summarize and curate the alien-specific information in the Darkness Revealed and Alien Encounters series. It does this through short, in-character narratives about Aeon operatives running afoul of the setting's aliens.
Taken on it's own terms, it's pretty entertaining, but as a strategy for the line as a whole, it's a disaster. There's a Qin embassy on the Moon. But information about the Qin is scattered through a half-dozen books, so you can't just add Qin to a game that uses Luna Rising. You've got to have them all, in order to piece things together. Then you have later books taking for granted that you're all caught up and if you read them out of order, you'll be baffled by the gaps.
Ultimately, this was a nifty bit of fiction, presented in an appealing glossy pamphlet form, but it doesn't tell us enough to be particularly useful as an rpg resource. Too much is being held back for future Trinity books that never got written. There are plot hooks here, but none of the worldbuilding necessary to flesh those plot hooks out. It's more of an invitation for GMs to write their own version of the Trinity setting than an attempt to explain what that setting actually is.
Also, the rape aliens are back and they don't really work better here than they did in the core. I guess they're meant to be these sci-fi horror creaures, creating monstrous hybrids of human-alien DNA to control our minds and enslave our society. And I guess it's pretty effective. If I saw a movie about the Coalition, I'd be scared.
It's just . . . sometimes I wonder if White Wolf forgot that it was making rpgs. If I'm the storyteller, I've got to look my friends in the eye and tell them what happens if the aliens catch up to them. And while I probably would have done it without hesitation back in 1998, in the year 2019, it's pretty fucking awkward.
UKSS Contribution: Hoo boy, I've not got a lot to work with. For all that this was an interesting look at Trinity's aliens, there's not a lot of depth or nuance here. None of the incidental details that I usually like to latch onto. I'm pretty much left with no choice but to include one of the alien species themselves.
I'll go with the Chromatics. They're lizard-like creatures with the ability to psychically manipulate light. They're a stone age culture, but the missing aliens, the Doyen, technologically uplifted them and drafted them into a fight against humanity.
I'll probably leave that last part out, but glow-in-the-dark lizard illusionists is something that I can definitely use.