The Hitchhiker's Guide to the Galaxy, overall, seems to be a bit of an underrated story, or, if not underrated, a story that a lot of people enjoyed but seem to have forgotten about. It deals with concepts of reality and what it means to not only be a human being, but a being at all. It blends cynicism and optimism in a palatable and engaging way. It has a diverse set of characters with motives (or lack thereof) that you don't normally see in scifi. It's consistently funny in a way that's bleak or "dark" but overall innocuous. And most importantly - it's downright odd.
My first exposure to it was the movie, a long time ago. While the movie most certainly stands up today, it was more the "long time ago" part for me that had me a little perplexed by it. I didn't understand a lot of the concepts, like the Earth being destroyed for such a menial thing as a galactic highway, I couldn't get into that perspective and didn't like that idea.
A few years later I saw another scifi movie that upset me even more - Melancholia, a movie about our planet's annihilation. Only, that movie is much more of a bleak character drama leading to Earth's demise. I hated the idea but it later made me think of Hitchhiker's Guide again. It's not the end of the world, and if it is, it doesn't mean we never existed, that our lives meant nothing. They do to us, and in the end that's what matters the most.
And so I came around to "odd-fi", and I further left the concept that scifi can only be about ships and lasers. It didn't affect me in the way Blade Runner had, which opened my eyes to the overall genre being much more than the sum of its parts, but it showed me that scifi can be funny without being hokey, or cynical without being depressing. It gave me a great perspective on a widened galaxy of storytelling in the scifi genre as a whole.