Eight students of telepathy go mad and their instructor is a vegetable. That makes the instructor the perfect person to work out the bugs in his system.
That the gentleman in question was a nut was beyond question. He was an institutionalized psychotic. He was nutty enough to think he could make an atom bomb out of modeling clay!
Spaceships. Orbital stations. Virtual worlds. Incomprehensible aliens. A pan-galactic society where humanity is a minority. Humanoid robots. Artificial intelligences. Journeys beyond the universe. Time travel. Psi powers. Space battles. Distant gods. Video games. Servers where one can live their afterlife. Utopian societies. The Blind Gods have all this and more.
Consider the poor mailman of the future. To "sleet and snow and dead of night"--things that must not keep him from his appointed rounds--will be added, sub-zero void, meteors, and planets that won't stay put. Maybe he'll decide that for six cents an ounce it just ain't worth it.
After some sudden and unspecified catastrophe has depopulated England, the countryside reverts to nature, and the few survivors to a quasi-medieval way of life. The first part, The Relapse into Barbarism, is the account by some later historian of the fall of civilisation and its consequences, with a loving description of nature reclaiming England. The second part, Wild England, is an adventure set many years later in the wild landscape and society.