Thank the Invader Nicely Dear:
Jim Ballantine, The Boy Who Saved Earth (New York: Del, 1979)
Pamela F. Serviss, Under Alien Stars (New York, Ballantine, 1990)
The reason I've paired these two books--apart from them being slim enough to squeeze into an overcrowded suitcase last Wednesday--is that they both posit the same thing; that we should be grateful when an alien race rescues us from a war they brought to our door in the first place.
That said, they are very different books. The Boy Who Saved Earth is, as you might expect with that title, strictly by the numbers and in some ways a hangover from the stiff upper lip of the 1950s. When fourteen year-old Marcou crash lands on earth he does very little crying over his dead uncle and crewmates but sets about learning English and Electronics as fast as he can so he can communicate with home and get help for when the enemy aliens land. It's passable adventure with very little science. Marcou's people are essentially just like us--second heart notwithstanding--and apart from a dig at the unkindness of the military there isn't much political happening here.
Serviss's book is more complex: Earth has been invaded, but we aren't actually important enough to be colonised. No, we are one of those off shore islands that happens to be strategically important in an inter-galactic war. It was a tad annoying that the invading aliens--to whom we will eventually be reconciled--were maroon humanoids with claws, while the nasty alien attackers where jelly blobs with fringes, but that apart Serviss took the opportunity to raise some interesting issues.
The book starts with the death of Rick and his parents while they are at a Resister meeting, and then moves onto Jason who resents his mother's collaboration with the invaders, and to Aryl, daughter of the Commander. There's an interesting conversation in which Aryl points out that they are treating the Earth better than Europeans treated the American natives, and also quite a lot of discussion about what Earth is losing v, what it's gaining, in which we are required to realise that Earth is losing less than the Resisters think (ie mainly pride) but that they are also gaining less in the way of technology than the invaders promise (ie they get to use it but not to learn how to make it).
Jason's mother turns out to be a Resister involved in a plot to capture Aryl's father. It's successful but one of the Resisters invites the other bunch of aliens in, in order to up the ransome stakes and it all goes horribly wrong. Jason and Aryl save the day, blowing up one of the invading ships and showing that humans and aliens can work together if...
... get this...
the Earth is completely colonised instead of only a military base.
Hard to know whether to laugh or cry.
But if you can find it, I would recommend the Serviss: the children are independent, they act like real people with real stresses and tensions (I think some of Serviss's ideas about alternative social structures just don't function but at least they feel odd) and there was a sense that science--and the possible halt to scientific development that comes with the initial invasion--do actually matter.