First to Fight is essentially a science fiction re-telling of Black Hawk Down. Admittedly, that's a loose analogy, but there are a large number of parallels. The story is set in the 25th century and the confederation marines serve as rapid response troops to deal with strife on the many worlds colonized by mankind, dealing with everything from religious warfare to piracy to insurrections to humanitarian aid. Like many similar stories (take your pick from Ian Douglas, Heinlein, or Steven L. Kent (and many others)), this starts as the story of a young man who signs up and goes through the rigors of boot camp and learning the realities of life in the marine corps. Gradually, it shift focus more and more to his platoon sergeant a grizzled veteran who has a bad tendency to get himself demoted for being a bit... overenthusiastic at protecting his marines. Anyway, the Marines are called into action due to a humanitarian crisis on a hell-hole of a world where everybody has been dumping their psychotic warlords and overly-combative tribesmen (including a good number of Somalis) for the past couple centuries so they can blissfully murder each other without troubling the more civilized universe. However, thanks to the planet's mineral wealth, the locals get access to more powerful weaponry and step up their ambitions, slaughtering and starving the planet's less bellicose citizenry, which leads to the planet's sometime government to beg for confederation intervention. Thanks to the complexities of the local politics and the planet's extremely inhospitable environment (not quite Arrakis, but there are parallels), the marines have their work set out for them, the more so since the locals have secretly stashed some advanced weapons.
First to fight is a decent space marine story, but it really isn't anything special. The story itself is interesting, but not particularly intriguing. If you're hoping for interesting alien worlds, bizarre alien cultures, political theorization, or sci-fi action, then this really isn't going to sate you. Frankly, apart from a couple of techno-gizmos (and plasma guns), the marines in this book fight about the same way American Marines did ten years ago (and in some ways the story seems pretty dated already; the UPUDs, in particular seems amusingly quaint compared to what your average iPhone can do and their problems with field communications seem sadly backwards for an interstellar civilization (ever heard of tight-beam?)). Sure they go from planet to planet in spaceships, but the spaceships aren't that important (in terms of how they fight), the planets aren't all that alien, and they're always fighting humans who are equipped with (at best) modern technology. As for political theorization, Sherman's only real contributions are a bizarre pair of diatribes for and against possession of firearms by civilians. They mention a Second American Civil War and their Confederation, but if you're hoping for some interesting vision of the future, Sherman simply doesn't bother filling you in on what exactly any of it stands for. The parallels with the failed Somalian Intervention of the early '90's also give the story an awkward aspect as his "everything worked out" ending doesn't match at all the way history went (not the Marines fault, but that's the way it is). This could be his point (in that he shows Marines basically running their own operation with ~0 political oversight rather than the chronically mismanaged Somalian Intervention), but I didn't really buy it. So all in all, Sherman has an entertaining (if pedestrian) story with fairly authentic-feeling Marine characters, but the setting and ideas simply don't live up to its predecessors in the space marine genre.