There are some authors you read in your late teens or early 20s and think are world-shattering and when you come back to them later you wonder why you bothered. William Burroughs was one for me - I'm with whichever reviewer asked 'can anyone over the age of 21 take this guy seriously?' or whatever it was.
Adams, though. I was very much taken with THHGTTG at a tender age - my parents recognised I think that this was a teenage infatuation, but tbh he is no Burroughs (in a good way) - the Guide is a spoof and intended as one, and a good-natured one at that. And as I later realised, probably influenced by Robert Sheckley's "Dimension of Miracles." But that was just a start point.
Perhaps such things as multidimensional mouse-like organisms, Vogon Poetry, Magrathea (every time I encountered the automated air defence system on the Ice Islands in SimplePlanes I thought of Magrathea's surface-to-space missiles defending a dead planet), "Your Plastic Pal who's Fun to Be With", knowing where your towel is, and so on and not forgetting 42 - has all become so much a defining part of cultural history for a certain generation that you really don't want to re-read it, not because it wouldn't be good, but because basically you don't have to.
Life. Don't talk to me about Life.