Have you already posted the other 23 chapters? If not, I would consider inserting more bits about the aliens throughout those chapters instead (if the story structure permits), so that it's not just one big explanatory thing all at once. But if each of your chapters is a specific POV, or have already been posted, I suppose that's difficult to achieve.

In that case, I would consider saving some of it for future chapters and working it in slowly, if it's possible (and it may not be).

What is the motivation for the aliens to invade Earth? Are they just evil, or is there some underlying reason that we--or at least the main antagonist--might sympathize with, since I'm assuming that he's a human and not actually an alien?