In a universe where space travel is commonplace and has been for aeons the extinction of a single species such as man is no big deal. So it was in this book. For some reason or another some aliens cause a Noah's Flood event here on earth. A single man survives and decides to find the answer to the eternal question.
"Why are we born to suffer and die"
Our hero wanders the galaxy. Answering this question is difficult as the creator got bored and threw this universe away like last years used up calendar long ago. After much searching the galaxy our hero, the last remaining human, finds a race of beings so old that they were around before the creator left so they know a few things.
The ancient ones answered the question and the answer is buried in the 42 letter sequence I created below. I don't want to spoil it if you find a copy of Venus on a Halfshell but if you want to find the answer to the question you are looking for two words run together. Six letters total.
I recall our hero had a companion who was an alien who resembled a woman, well enough for our hero to be happy. I could be wrong about that. He also had a dog.