Watchers of the Dark
Watchers of the Dark, by Lloyd Biggle, Jr.
Happy January! For my first vintage SF pick, I went with this mystery title -- meaning I didn't know a thing about it -- which I got off the donation table some time ago. It's a 1st edition from 1966 in near-perfect condition; I'm not sure it's ever been read. I didn't expect it to be very good, but in fact it was really fun, a combination of a hard-boiled private eye story and interplanetary SF.
Jan Darzek is a New York private eye in 1988, which is just like 1966 except you can teleport instead of taking the subway, which sounds very handy. A Mr. Smith offers Darzek the job of a lifetime -- very dangerous, will take years at best, but the client will pay anything. Darzek's secretary, Shluppy, insists on coming along (she is Miss Schlupe, a tough little lady in her 60s who is worth reading the book for all by herself) and they find themselves on a space transport, headed for the center of the galaxy.
There are zillions of inhabited worlds, and if they're civilized enough, they're allowed to join a peaceful wider galactic society. So there is an incredible variety of life-forms of all shapes, sizes, smells, and dietary needs, and they carry on complicated trade networks. Now, however, the Dark is making inroads into the galaxy, and nobody knows how to stop it. Worlds go suddenly mad, and then dark. They still exist -- it's not the Echthroi or the Nothing -- but they're incommunicado, and they destroy their spaceports. Darzek, being from an uncivilized world, is hired because maybe he can figure out what the more peaceful species cannot -- what is the Dark, why is it invading, and how does it work? Can it be stopped at all?
This is a really fun detective/spy adventure in space. Biggle doesn't explain much ahead of time, which is how I like it. He obviously had a lot of fun inventing the widest variety of beings he could think of! If you made a movie, it would have to be animated.