Although the scene of an SF universe can sometimes be a bit tedious, the world and Douglas Adams characters are so crazy and funny some attention willingly. I loved especially the character of Marvin, depressed robot. As in any utopia, this imaginary world can serve to social criticism or even a philosophical reflection although I would say it is still a bit limited here in the sense that thought tends to disperse in the most fantastic way.
While some consider it "space opera" as a cult series, I do not go that far personally. Nevertheless, I recognize that meets certain criteria. First, he inaugurated the genre of humorous SF. Second, his sense of the absurd (or rather the "non-sense" as the English say) is worthy of Monty Python. Third, it gives the answer to the ultimate question about life, the universe and everything (42 for those who can not survive the suspense).
A little quote to finish ...
"- What's happening It's not very clear ...
- I can not tell you - I feel myself quite dark. "