(Yes, "42" is cute, too, but you have to read the book (five of them, in fact) to get close to understanding what it might possibly mean. And since the computer built to calculate the question for this answer crashed, nobody may know for certain.)
Kurt Vonnegut writes:
So, I am going with Kurt's advice and posting it in order to have it handy next time someone asks what the meaning of life is. I don't think I can forget it.
"I put my big question about life to my biological son Mark. Mark is a pediatrician, and author of a memoir, The Eden Express. It is about his crackup, straightjacket and padded cell stuff, from which he recovered sufficiently to graduate from Harvard Medical School.
Dr. Vonnegut said this to his doddering old dad: “Father, we are here to help each other get through this thing, whatever it is.” So I pass that on to you. Write it down, and put it in your computer, so you can forget it."
Sometimes you just have to have a simple answer. Not as simple as "42", but it will have to do.