Manifold is not a series per se, but rather different explorations of the theme “Are we alone in the universe?”. In “Time”, a portal is discovered in the solar system, and some fascinating stuff happens related to preserving life and intelligence in the long term. In “Space”, The Fermi Paradox is suddenly reversed, with aliens appearing everywhere and the whole universe is just one big fight for resources, to the point of utter barbarism.
I had some nasty nightmares after these, which is why I will probably never read the third book, “Manifold: Origin”. On a certain level, this is very stuff, but not like a horror movie. It scares me on a very deep level that I can’t rationalize away. The same level that knows that the goody two-shoes future of Star Trek simply is not a realistic vision. Still, I would rather watch Star Trek since I don’t want to wake up screaming in the middle of the night, however good Baxter is. Read the books if you feel you can take it. They are very good and the themes and subjects are both engrossing and fascinating.