It doesn't touch everyone. When I was 11 years old (in 1984) they were a revelation to me. Like someone finally wrote something just for me. My son is a voracious reader, and I encouraged him to read them, but he just said "this is weird" and put it down after 5 pages.
Thinking back on it, I was introduced to the radio show first (I had a 2nd generation bootleg, on cassette). Maybe that made me ready for the characters?
I remember attempting to read the Guide sometime in highschool and found it nonsensical and not fun at all. When I picked it up again several years later I enjoyed it immensely and read the entire series. I guess you need have a job and first-hand experience with neighborhood plans publicly displayed behind figurative "Beware of the leopard" signs to appreciate the humor.
Thinking back on it, I was introduced to the radio show first (I had a 2nd generation bootleg, on cassette). Maybe that made me ready for the characters?