The Hitchhiker's Guide to the Galaxy is the first book in an awesome series by Douglas Adams. I really enjoyed the fourth book in the trilogy, mostly because it was the fourth book in a trilogy....anyway, as the story goes, long ago there was a group of super-intelligent beings. They wanted to know the Ultimate Answer to the Universe. So they built this supercomputer called Deep Thought and it took 7.5 million years to calculate the answer. The answer is 42, and that's all Deep Thought had to say about it. It was unable to produce the Ultimate Question to the Universe.
So an even more powerful computer was built, and that was the Planet Earth. These pan-dimensional creators of both Deep Thought and the Earth took the form of mice. Humans are actually a race alien to Earth that crash-landed here and made the process take longer than it needed to. After 8 million years, 5 minutes before the answer was completed, Vogons (a nasty alien race) destroyed Earth so they could have a better superhighway through hyperspace.
But that's not the end of the story. Arthur Dent, the only surviving human from Earth, has the Ultimate Question subconsciously stored in his mind. So after escaping Earth's destruction and embarking on trippy adventures spanning the universe and including time travel to the end of the universe (specifically to a restaurant where you can watch the universe end in glorious fashion over and over again), he wound up traveling back in time to when the Golgafrinchons (our ancestors) crash-landed on Earth.
The subconscious question was drawn out of him by drawing random Scrabble tiles. The message said "What do you get if you multiply six by nine?" The answer is obviously 54, but Deep Thought's answer was 42. Dent sees this and says, "I always thought something was fundamentally wrong with the universe." Never mind that the Scrabble message included 3 Y's, and an ordinary game of Scrabble only includes 2. Maybe he drew a blank. Or maybe it doesn't really matter.
People have tried to read way too much into this. It's just Adams being funny, and 42 seemed like the funniest two-digit number he could think of. The only really plausible hypothesis that I've seen has to do with Base 13, which means you take any number in the tens place, multiply by 13 instead of 10 (hence base 13), and add to that whatever is in the ones place. So look at the Deep Thought answer: 42. Take 4 X 13 and that's 52, add two and that's 54. And 9 X 6 actually is 54. Adams heard this theory and said, "I may be a sorry case, but I don't write jokes in Base 13."
Anyway, you should read these books. They are incredible and may change your life.