Something I really like about Douglas Adams' writing, aside from just the overall funniness of it, is his knack for description. He has all sorts of wonderful, glisk-inducing phrases that absolutely delight me, even when he's describing decidedly un-delightful things. For instance:
It has been said that Vogons are not above a little bribery and corruption in the same way that the sea is not above the clouds.and
The hands that held the curtain were long and thin too: they were also cold. They lay lightly along the folds of the curtain and gave the impression that if he didn't watch them like a hawk they would crawl away of their own accord and do something unspeakable in a corner.Of course, the thing that made me and Mom absolutely collapse was a complete throw-away line about "routine towel maintenance." You had to have been there, I think.
Fans of Douglas Adams really must read The Salmon of Doubt. In addition to containing the fraction of a novel he was working on when he died, it has a collection of other writings on a number of topics, both humorous and serious. It's fascinating to see how his style comes through in letters, articles and essays, and you can see what a genius the guy really was.
At some point I also want to find a copy of the original BBC radio version of H2G2. That would be really cool to listen to.