I read that Inherent Vice was Thomas Pynchon’s sequel to Vineland and cringed. Inherent Vice was a silly, weak-assed fictionalization involving the sub-cultures surviving in the Los Angeles area, including the surfer crowd and lots of drugs. Vineland was about the survivors of sixties subculture in California but there the comparison, stretched as it is, ends. Vineland is a well structured novel with a narrative that is varied by character, loops back regularly on critical events, and involves just enough otherness to leave the reader with some concern for the generally realistic elements of the narrative.
Like so many novels, Vineland is enhanced if you have some experience with the events and locations that it presents. If you have no experience with Hippies or the lure of Northern California communes (now very newsworthy for the quality of the bud grown on the foggy mountainsides), then parts of Vineland are going to be less immediate than they would be to a Wavy Gravy (for instance).
But Vineland isn’t a novel of the sixties with the Merry Pranksters and love beads; it’s a novel covering the start of the Reagan era of greed and mendacity involving overly zealous government types and aging hippies. The cover writeup from the Penguin edition gives a good summary: