Alright, SCIFI GEEKS: I need recommendations for gritty, military scifi novels focused on repelling some sort of alien invasion. Ideally with dubious moral choices and truly *alien* adversaries... GO!
Define "truly *alien*."
If it means "psychologically completely unlike humans", what you have is a "bug hunt" - there is no common ground for any other kind of interaction, and at least one of the two parties is unwilling to peacefully coexist.*
If it means "physically unlike humans, but with at least some psychological common ground to allow interaction", then I second "Mote in God's Eye".
*It takes two to make peace, but only one to start a war.
Thanks, guys--this is great! I'd forgotten about Footfall, which probably comes closest to what I'm looking for (I forgot to mention the invasion needs to be of Earth...)at the moment. There are surprisingly few novels (though MANY movies) about aliens invading earth before we're capable of getting out of the solar system (or even to Mars...)
As for "truly *alien*", I guess I'm going for just barely relatable, like in that recent Tom Cruise movie where he's traveling back through the same temporal path over and over. Those were (I thought) awesome aliens...
We have seen the black suns / Pouring forth the night. --Clark Ashton Smith
My favorite is the already mentioned Starship Troopers. However, another one that is quite different from most other sci fi stories is Harry Turtledove's World War series. The antagonists aren't really too different from humans, but the interesting thing about this series is that the aliens invade while Earth is in the middle of WWII. There is a bunch of interesting things like the axis & allies calling truce to deal with the aliens. Certain human factions aligning with the aliens, and etc. It takes quite a bit of reading and spans 7 or 8 books that range from WWII- the early 21st century. I used to be quite into Turtledove's stuff. IIRC he's a history professor and he goes into highly researched detail about his historical settings and his characters are for the most part, quite compelling.