When America first discovered that there were aliens, the aliens told them of another set of aliens named the Dreen, who were an implacable threat. With the aid of a black-box hyperdrive from the aliens, the humans remade a submarine into a spaceship named the Vorpal Sword and took it into space to help their alien friends.
The mission was a success, but it came at a high cost. Seven out of every eight marines on the ship died in various conflicts, along with most of the scientists. One set of attacking Aliens, the Mrrr, turned out to be slaves of the Dreen, and were taken out. The humans also found a way to close the gates to the Dreen worlds, by detonating a nuclear bomb on one side of the gate.
Now refitted, the Vorpal Sword is returning to space to investigate an attack on a world that archaeologists were investigating. There was a gate there, but if the Dreen are on the planet, opening it from the earth side would be foolishly suicidal, so instead the Vorpal Sword is given the task of going to the world.
Along for the ride are Marine Eric Bergstresser, who actually managed to survive their last trip and feels he may be falling in love with a girl from back home, William Weaver, PH.D. in Science and the only man who has come close to understanding the nature of the hyperdrive on the Vorpal Sword, along with a host of new officers, NCO's and marines who will have to adjust to and survive their trip back into space.
The Ship must not only survive the trip to the planet, but the encounter with a new species and a fight against the Dreen once again, this time against the biggest ship they have ever encountered, a Dreen Dreadnought.
I really enjoyed this book, being a sucker for military-style SF that started with David Weber and the Honor Harrington books. In fact, John Ringo has been David Weber's co-writer on a number of books, and I picked up this book solely for that reason. Thankfully, I wasn't disappointed with this book the way I was by "Sister Time", another book that John Ringo wrote.
The Dreen are pretty scary as a race, and when we finally see the inside of their ships, they are just as scary, with some kind of fungus that they use to control various points inside the ship and weaponry that seems as much grown as built. Plus, the fact that they vastly outnumber the population of any one planet, and they are much, much more advanced than Earth technology maks it clear that we, as a species, have our work cut out for us when we are trying to survive. The only thing that has saved the earth so far is that the Dreen don't know where Earth is located, and, luckily, they have not yet been able to backtrack the Vorpal Sword or any other information humans have taken out into the stars with them. Based on what happened on the planet the Sword was dispatched to, however, that may change in the future.
If you're on the lookout for a good military SF book, "Manxome Foe" does not disappoint.