I'll put in my two cents and say Douglas Adams was a genius with a great and remarkable sense of humour, who wrote quite a few highly amusing books. I am still grateful to Grondy for introducing me to his works and can only recommend them to anyone else. They are, in short, :funnylaugh: . Apart from the HHGTTG series, he also wrote a few books (two, I think) on Dirk Gently, a rather conspicious private detective. The books are called Dirk Gently's Holistic Detective Agency, and The Long Dark Tea-Time of the Soul. (off the top of my head, do please correct if wrong)
There is also "The Salmon of Doubt", a compilation of various of his writings, including part of a manuscript he was working on shortly before he died.
And then there is "The meaning of Liff" and "The deeper meaning of Liff", and a book of which I have forgotten the name, on threatened animal species, if I remember correctly.
As for his books, I like the Guide series best. High time I listened to the radio series, but they are quite hard to get hold of when you live in a rather forsaken part of the galaxy like I do.
*clicks link above*