The first two books in this series about a Space Marine NCO, Torin Kerr, Valor's Choice and The Better Part of Valor, were really excellent, which is why I sprang for this one in publisher's HC as soon as it came out. This one was still quite enjoyable, but not as good as the first two, imho, and if I'd known that I'd probably have waited for the PB in a year or so. Torin has been promoted from Staff Sergeant to Gunnery Sergeant and is giving a course on the Silsviss to various Marines at a training base on a space station. A Major she'd worked under in the first book, who'd been so badly injured that his life had barely been saved and he'd spent two years in a regrowth tank and had just recently been decanted, has persuaded the brass to send him with a recruit platoon to Crucible, where recruit classes are sent for a 2-week tactical problem as the last part of their basic training. But under the condition that his attending physician goes with him, and that Torin accompanies them for added protection. Then when they get there the senior DI on the mission goes into a change peculiar to his species, and he's the only one who can abort the mission--and the various drones that act as enemy on the missions, with tight restrictions on how much damage they're allowed to do, start seriously attacking the platoon. And the orbital platform that has the capability of turning them off is destroyed by a SAM. And then things start to really get interesting. Meanwhile, Torin and her sometime lover, Craig Ryder, have discovered that they are apparently the only ones who were on Big Yellow, the alien spaceship, who remember that an escape pod from that ship was picked up by the Confederation ship they were on, and while Torin is on Crucible Craig investigates that, with surprising results. It's a good story, with an interesting mystery to go along with the battle action; it's just not up to the level of the first two books (which, if you missed, are now out in an omnibus titled Confederation of Valor).