Yeah Destroyer is awesome. We played it last year over a period of several weeks and had a ton of fun. It's essentially the second part of a trilogy that began with Chariot, though you don't have to have played that first in order to understand it as Destroyer features completely new characters in a different setting (there are just some story points that call back to Chariot that you'll recognise if you played that first).
As people have said, the characters are all Colonial Marines stationed on a colony base who are tasked with finding some awol fugitives on the eve of an invasion. It's a lot longer than Chariot and is very much an "Aliens"-inspired adventure as opposed to the "Alien" influence of that one. So lots more action, lots more big guns, lots more creatures, and a lot of really cool twists that led to a lot of great "ohhhhhh ****!" moments.
It's really fun and definitely worth playing if you liked Chariot or the rpg in general (especially if you've been itching for more smart guns and apc's to play with). Just make sure you set aside plenty of time to get through it, as it's probably about twice as long as Chariot is, with each act feeling like a mini adventure on its own.
