This is the kind of story that Star Trek is all about. Meeting new species and facing the hardships that may come with that. The Latter Fire is a fairly simple story, and the characters all feel true to their on screen persona... except maybe Scotty, but perhaps that's just me. The write up provides all you need know going in, so I won't get in to that, but the most common complaint I've noticed in the reviews is that TLF is predictable. While there are certainly plot elements that some can say they've seen before, there's still plenty of surprises to make up for that. I did however find a few things that caught my attention:
The first is that there is a civilian-ran diplomatic corps. I don't know if this is a new thing, from the mind of the author, or if I simply don't remember any reference to it. Regardless, why do we need a diplomatic corps that's separate from Starfleet if they don't have any of their own resources (ships, supplies, security...)? Seems a little redundant when there's six ST shows where SF officers do diplomatic work. There's also a scene that takes place in the brig, and it uses a force field to contain the captive audience. I don't believe TOS-era ships used fields for their cells just yet, but the only evidence I have off the top of my head is ST V so that may be a non issue.
My biggest criticism is of the book's antagonist. Memorable villains are those who the reader/viewer can understand their motivations, and even empathize with their actions to some degree. The one here was so rigid and malicious that he became insufferable very quickly. There are definitely people like him IRL, but they make for poor fictional characters. Nobody would ever take a person like this seriously, and the dialog to/about him because tedious almost instantly... actually there's several conversations that discuss the same things multiple times. The climactic action scene would've been better if it was something other than including the villain one last time, IMHO of course.
Other than those nitpicks, I highly recommend this book to the hardcore and casual fan alike. There is some genuinely interesting things here that will be new to a lot of people. It's also very refreshing to read a ST book that actually feels like Trek. Live Long and Prosper!