In the future, there are two primary states on Earth, plus others on Mars, Luna, and the Belt. We've found a star tunnel from an alien race that has interesting properties. We've met a lot of other humanoid races -- differing from us by very small amounts -- and one of them, rather than saying "hi," is trying to kill us. We've never spoken to the Fallers (no idea where that name comes from) or seen them, but they're trying to kill us.
We're sending anthropological teams to the planets with people like us and the prologue starts with the all-powerful military guy for Earthspace getting some kind of notice about one particular planet. Another team is sent, but along with them is a retired scientist and staff because the first team found that one of the moons is a manufactured item, made of materials like the space tunnels.
The book has two stories -- what happens down on the planet as the team struggles to seem welcome to a race that has "shared-reality," and what happens in space as the moon is investigated. All the action is in the last part of the book and while it reaches a sufficient ending, it's not a very satisfying one. I suspect you should plan on reading all three books to really get the story.
