Humour is what drew me to it the first time I read it. A friend pointed out that there are some hidden jokes that only make sense when you already know how it will end, so I read it again, and again... And kept discovering new layers. With years (I take it in my hands from time to time) these discoveries became a rare occurance, but I'm quite sure I still missed some of the gems. And it took some growing up to understand some of the messages.

Adams really was a master of observation. Especially if you consider that many things we take for granted today either didn't exist or were in very early stages (like Internet). Predicting basically "wikipedia on a phone" that far back is mindblowing. And of course, the exaggerared (but still believable) characters are a work of genius.

Maybe give it a second chance if you have spare time?

That said, I only read the last book twice because it makes me depressed. Ymmv of course.