I wish Joe Haldeman had credited in some way the original book, one I read as a teenager 40 years ago or so. I don’t recall the title or author, but will try to find it. I can’t rule it out just now that a very young Haldeman might have written it. Almost every detail about the crystal teleportation technology and the ways humans and aliens use it and react to it are duplicated. Even gravitational detection of the alien starships in Earth’s neighborhood was there in the original. But I admit Haldeman’s version is more thoughtful and satisfying. It’s a fun book. Thumbs up.