Two of his books which I haven't seen mentioned are, Dirk Gently's Holistic Detective Agency and The Long, Dark Tea Time of the Soul. Both of which I found funnier than the later books in the 6-book Hitchhiker's trilogy. Despite, the humour, they had some very useful advice. One such passage was on the Zen art of driving. If you are lost, you follow someone that you are pretty sure is going where you want to go. I have used this technique without fail a few times (god forbid I ask for directions!)