Sci-Fi/ Fantasy book at least 40 years old (before 1984): Scientist goes off to visit ex-girlfriend in her friendly but very insular US Southwest home-town. Town runs on a local fungus. Spoilers ahead

[Tim]

A bloke's a young beginner scientist at some uni or suchlike in the American Southwest. He gets a letter from an ex-girlfriend he knew in college. Him and the girl broke up (IIRC, and only if IIRC) because she refused to permanently leave her hometown, in some Southwestern valley. While in college, away from her hometown, she made sure to regularly eat sandwiches (or something, I forget) sent to her by her family. scientist bloke decides to check out girl's hometown for first time (because of letter?). So off he choofs there. He discovers it's a very friendly but very insular town. Big chainstore businesses try to open there, but always fail, and leave. Scientist discovers a unique local fungus growing (in the canyons around the town ?? In caves there?? I forget). He suspects this fungus lies behind what seems like almost group-telepathy of the town. He decides to research the fungus. No-one stops him. He feels a mental compulsion to eat/taste/huff the fungus, but he can resist it. For the research, he finally prepares a heap of purified, isolated fungus. The mental compulsion becomes over-powering; he scoffs (gulps) the lot down all at once. And nearly dies. The girl, now a woman, comes into his makeshift lab just in time to get him to treatment. Afterwards, she explains to him he OD'ed badly on the fungus, but she & townspeople take care to eat it regularly in small doses, as on the sandwiches? sent to her when she was in college. The fungus provides the townspeople with a limited group telepathy or consciousness; and they simply otherwise lead normal, happy, human lives, but never stay too long away from their town. Assumedly, he + woman marry & he settles down in town forever.

The book would be at least 40 years old. Sorry I can't remember more. Many thanks in advance for all help on this.

[Capn]

Have you scrolled through the "Fungus Fiction" list already? :)

https://www.goodreads.com/list/show/1...