A Heritage of Stars

Novel, first published: Berkley/Putnam 1977

It is the year 3952 A.D., with all technology having disappeared five hundred years before. All books or even allusions to technology have been completely eradicated, and after an initial period of chaos, the world has returned to a tribal anarchy. The protagonist, Tom Cushing, is a student at the university, where a library and basic literary skills are preserved. Tom leaves the safety of the university walls to pursue a tantalizing myth - The Place of Going to the Stars.
As in all of Simak's quest stories, his favorite pattern for all his later novels, Tom is joined by the usual heterogeneous company: a telepathic "witch", an errant robot who has broken his inhibition against killing, an assortment of aliens, and an old man accompanied by his psychic granddaughter. The company gets help from some living rocks and some sentient trees resembling the music trees in A Choice of Gods. (In his later novels, Simak replaced dogs with trees as the inheritors of the Earth.)
After a number of narrow escapes from hostile nomads and grizzly bears and a series of close encounters with more wonderfully imagined aliens, the company is admitted to the Place, which turns out to be a city guarded by the trees. A huge robot appears and explains that humanity did go to the stars and brought back some of the aliens the company met along the way. A small group of scientists and engineers established the Place as a library for knowledge gathered from other civilizations in the Galaxy, but the retrieval system is not working. With the help of the psychics, this knowledge could be tapped, technology rediscovered, and humans put back on the track. The story should end here, but Tom, like Natty Bumppo, goes into the nomad village and gets himself captured - then rescued in the nick of time by his grotesque buddies.

Ewald, Robert J.: When the Fires Burn High and the Wind is from the North, p.111-112