This book contains three unrelated stories (and I should warn that my reviews contain major spoilers):
Host Age (1955)
This story is pretty great! A mysterious plague has broken out in London; it infects 10% of the people who are exposed to it, and 10% of those infected die. Antibiotics don't work on it, and attempts to find a vaccine have been unsuccessful. The protagonist is a doctor who's the head of a clinic that treats people who have caught the plague and is friends with the head of a biochemical company that's trying to find a cure for it.
Various bizarre things happen, and the doctor gradually (well, somewhat gradually; if I have a complaint about this story it's that his deductions come a lot more quickly that is really credible) comes to realize that the disease is being spread intentionally by people from the future. Ultimately it's explained that the disease was unleashed by another race that humans came into contact with in the future and is uncurable. Since by that point in the future all disease had been eliminated altogether, humanity's immune systems were completely unprepared for it and it killed 99% of them.
The solution: go back in time (using a technology fortunately unknown to the enemy race) and introduce the disease at a time when world travel was common enough that the disease would be spread far and wide and when disease was still common enough that peoples' immune systems would have a better shot at resisting it. This would have two results: First, when the enemy alien race unleashed its weapon against humans, they would already have evolved a resistence against it. Second, since no vaccination is fully effective against the disease, humanity would never be fully rid of it, so the human immune system would also be somewhat prepared for other attacks of that sort.
It's a neat idea and is executed well, and the final revelations came as a genuine surprise to me (although of course I've now ruined it all for you). We note that in this story John Brunner gets to kill off the human race twice, once through an alien invasion in the far future and the other through a present-day plague, which is a sort of twofer that even Mr. Brunner can seldom pull off. Well done that man.
Man, I feel so liberated by that 'spoiler' warning at the top of this message. The pivotal plot device: Everyone on the ship is deluded! Man, that felt good.
Anyway. A rich guy has spent a bunch of money setting up a colinization ship to go to a nearby star and settle. The story takes place many years after the ship left, shortly before it arrived. The original crew are getting up there in years and the actual colonization is to be done by their children, who, however, are not particularly eager to leave the ship which has been their only home.
There's lots of conflict and the original crew try to control their children using hypnotism, sort of, but it doesn't work. Then, the pivotal moment -- it turns out that the original crew was also subjected to hypnotic control before they left! Which is why everyone's been acting so nutty! It's like a mediocre Philip K. Dick story, only not as weird! Hey, we don't have to fight after all, let's find a solution that works for all of us!
The actual underlying idea, and the reason the story is called 'Lungfish', is that just as some fish left the ocean and found home on land, so this new generation of colonists would leave land and find a new home in space. It's not a bad idea but I didn't find this story very engaging.
No Other Gods But Me (1966)
This is apparently based on an earlier, much shorter story from 1956 called A Time To Rend. It would be interesting to compare them, maybe.
The protagonist is of a type I've seen in other Brunner stories: depressed, worried he might be going nuts (arrrrrrr!), kind of a jerk. While waiting for a bus in London he runs into a mysterious woman (also familiar from other Brunner stories) he remembers seeing in Australia, and they have a weird sort of alien abduction experience, at then end of which they've lost six hours of time. They go back to her apartment, and a guy materializes and warns them to stay the hell away from each other. Wackiness ensues.
Eventually we learn that there's a parallel Earth where, early on in mankind's development, a child was born with immense psychic powers, and that that child's descendents now control the parallel Earth and have designs on our Earth as well. The hero and heroine are important, because (the theory goes) their genes are such that if they had a child he or she would have the same sorts of powers and would be able to serve as a conduit between the worlds. I think. It's a little confused. Anyway, the potential of their genes is so high that just having them in close proximity is enough to make travelling between the worlds easier. To make it even easier, the leader of the alterna-world has influenced people in ours to start a religion worshipping him.
One neat idea is that since in the other world the ruling class has no real need of technology -- anything they want to do they can either do directly, through user of their psychic powers, or they can have done for them by members of the non-psychic underclass -- the technology there is stuck at Caveman level, and the guards there go around carrying big clubs, etc.
A general comment: One of the nice things about reading John Brunner books is that he has sizable chunks of humanity be destroyed in so many of his books that you can never be sure how a particular book or story will end. It lends additional suspense to them! (Which of course I'm ruining here.)
That said, in the end the whole thing turns out to be a false alarm and we learn that the psychic powers that are so powerful in the other world don't really work that well here, and the 'invaders' end up getting ripped to shreds by a street mob in Manhattan. (A nice line from the book, spoken by a random member of the crowd:
Isn't that a Pete Seeger song?)
God damn, this banjo will make a club!
There were some neat things about the story, and the characters were reasonably engaging, but enough things didn't quite add up right that I had trouble immersing myself in it.
In terms of civilization destruction, the Earth is saved from being conquered, but it's made pretty clear that the alterna-Earth's society is going to be torn apart completely after the loss of a fair chunk of its upper caste (although maybe that ultimately will be a good thing since it will let humanity continue to evolve 'normally' there). Also, humanity is actually portrayed in a somewhat positive light (at least we aren't enslaved to giant psychic cavemen! Think about that the next time you're complaining about John Ashcroft!).