Trial By Fire (Charles E. Gannon, Baen) is the sort of book that divides those who notice it into two parts. One group will sneer “Yard goods from Baen, yet another space opera full of stuff blowing up”; the other will nod and smile and say “Good clean fun, I’ll take it.”
I’m cheerfully in the second group, myself. But I do have standards. Done badly, this sort of thing is just boring and derivative button-pushing, a sort of male-targeted analog of formula romances. Done well, it’s a fun ride with enough elements of puzzle story and sense of wonder to make it respectable SF even if it doesn’t aspire to the heights of conceptual breakthrough found in the best of the genre.
This particular book is the second in a sequence that I would describe as enjoyable if unexceptional. Much of the furniture is familiar (one of the major alien species is perhaps too much like Alan Dean Foster’s Thranx, and another is fairly generic Proud Warrior Race Guys) but the author knows his way around the battles and action scenes, and some of the reveals in the puzzle side of the plot are genuinely interesting.
Overall, the author earns his money. You’ll want to read the first book, Fire With Fire, before this one. Expect sequels – but if you’re in the target market for this book, you already know you want them.