I haven't read The Hitchhiker's guide to the Galaxy, but doesn't it end without the people ever finding the answer, or something?
"Don't panic!" was on the cover of the book, wasn't it. So, that picture features space, Trials, and the book...
Just noticed that the rider is in some sort of a bathrobe, and that Don't Panic is his towel... What does it mean?!
Ford handed the book to Arthur.
"What is it?" asked Arthur.
"The Hitchhiker's Guide to the Galaxy. It's a sort of electronic book. It tells you everything you need to know about anything. That's its job."
Arthur turned it over nervously in his hands.
"I like the cover," he said. "'Don't Panic.' It's the first helpful or intelligible thing anybody's said to me all day."
The Hitchhiker’s Guide to the Galaxy has a few things to say on the subject of towels.
A towel, it says, is about the most massively useful thing an interstellar hitch hiker can have. Partly it has great practical value — you can wrap it around you for warmth as you bound across the cold moons of Jaglan Beta; you can lie on it on the brilliant marble‐sanded beaches of Santraginus Ⅴ, inhaling the heady sea vapours; you can sleep under it beneath the stars which shine so redly on the desert world of Kakrafoon; use it to sail a mini raft down the slow heavy river Moth; wet it for use in hand‐to‐hand‐combat; wrap it round your head to ward off noxious fumes or to avoid the gaze of the Ravenous Bugblatter Beast of Traal (a mindbogglingly stupid animal, it assumes that if you can't see it, it can't see you — daft as a bush, but very ravenous); you can wave your towel in emergencies as a distress signal, and of course dry yourself off with it if it still seems to be clean enough.
More importantly, a towel has immense psychological value. For some reason, if a strag (strag: nonhitchhiker) discovers that a hitchhiker has his towel with him, he will automatically assume that he is also in possession of a toothbrush, washcloth, soap, tin of biscuits, flask, compass, map, ball of string, gnat spray, wet-weather gear, space suit etc., etc. Furthermore, the strag will then happily lend the hitchhiker any of these or a dozen other items that the hitchhiker might have accidentally "lost.". What the strag will think is that any man that can hitch the length and breadth of the Galaxy, ruff it, slum it, struggle against terrible odds, win through and still know where his towel is, is clearly a man to be reckoned with.