The Ultimate Hitchhiker's Guide

"All you really need to know for the moment is that the universe is a lot more complicated than you might think, even if you start from a position of thinking it's pretty damn complicated in the first place," - The Hitchhiker's Guide 2.0

I cannot even really begin to explain to you how much I like this book. It is absolutely brilliant, that's the first thing I should mention. Something absolutely hilarious is happening on every single page, and all the while the plot is doing these amazing, twisting, things. The effect of this is that each individual sentence is gratifying while being part of an overall masterpiece and completely amazing read in general.
If you never read another book in your life, you should probably read this book. Or, rather, these five books, and a short story. Though the short story's not that important.
For the sake of making this blog easier, as it stands a pretty good chance of getting really complicated, I should probably clarify this right now: The Ultimate Hitchhiker's Guide is a novel composed of five other books that were all released separately. So, from now on in the blog, when I refer to "the first book" or "the fourth book" I mean the books within the work as a whole, and when I mean the novel I mean the overall story arc achieved by combining all the books into one work.
What I really want to examine, out of the millions of things to examine in this novel, are the two main points that I think Douglas Adams makes, whether he was even aware of it or not. The two main themes of the novel are: Attempting to define the universe, and trying to find happiness against the backdrop of utter infinity.

The attempt to define the universe is a constant presence in this novel. The Hitchhiker's Guide to the Galaxy, while being the name of the first book, is also a book that the character's carry around with them. It is a guide for all the travelers of the universe, and given the amount of universe that is out there and the time it takes to collect the information, the guide is almost always wrong about something or other, and makes no excuses for that. Similarly, it is mentioned briefly at the beginning of the fourth book that a census was put out for the galaxy, and it wasn't particularly useful because it just told everyone what they already knew. The only new information that the census provided was that all creatures have 2.4 legs and own a hyena. As this was obviously wrong, the entire census had to be scrapped.
Basically, throughout the novel it is made clear that there is a kind of utter futility in understanding the universe. One man, at the end of the third book, is given too much truth serum before going into court, and when he is told to tell the truth, whole truth, and nothing but the truth, he does just that. The end result is that he dies laughing.
Also, at one point we encounter the ruler of the universe, who is expected to know everything but in fact knows nothing. I mean, really, nothing. He talks to the table for a week to see what it does. He doesn't assume that anything he perceives is real because it's all just a perception, just sensory input that can't be trusted as truth.
One of the most classic bits in this book is that the answer to Life, the Universe and Everything is 42. This answer was arrived at by an ancient super computer named Deep Thought millions of years ago. The people that built him couldn't understand the answer, and Deep Thought told them that was because they had the answer but didn't have the question. In order to obtain the question, they would need an even more powerful computer, a whole planet actually, whose organic lifeforms would be part of it's hardware.
This computer was the Earth, but unfortunately it was destroyed five minutes before the answer, or rather the question, was obtained.
In short, the universe is never understood, fundamentally cannot be understood, and by the end of the novel as a whole, understanding it becomes so obviously impossible the main character, a fellow named Arthur Dent, isn't even trying anymore. All he's trying to do is be happy, and the way to be happy is to just not think very much.
Douglas Adams goes to great lengths to demonstrate that not thinking and not understanding the universe are the keys to happiness. In the face of utterly infinite probabilities and possibilities, in a universe where socket wrenches grow on trees on some planets and the improbabilities of restaurant mathematics can power spaceships, all one can really do is get drunk and lie on a beach with good looking women.
The two most consistently successful characters in the novel, Ford Prefect and Zaphod Beeblebrox, are adamant followers of this philosophy. Whenever presented with a major problem, their solution will inevitably be to escape the problem all together and get drunk. In fact, intentionally not knowing (and by this I mean blocking off an entire section of his brain) is how Zaphod is able to become President of the Galaxy and steal the greatest spaceship ever built. However, his success is sort of diminished by the fact that the knowledge he blocked off was that he planned to reach the ruler of the universe, who knows nothing, and thusly the whole point is pretty much moot.
So, it is clear that happiness is hindered by the attempt to understand the universe.
Not knowing also comes in very handy if you want to fly. Flying, this novel says, is the art of throwing yourself at the ground and missing. The way you miss is to become suddenly distracted at the last minute and forget that you're going to hit the ground, and then to not think about the fact that you didn't hit the ground or you will.

The utter down note that the novel ends on is this: In the complete infinity of the universe, no one fits anywhere, especially when multiple dimensions and parallel universes get thrown in the mix. Happiness is elusive and almost impossible to achieve unless you are completely ignorant of the rest of the universe and the complication and confusion it causes. Of course, once you are aware of it all, trying to settle down and simply make sandwiches for the rest of your life isn't really an option anymore.
This tone starts to set in at about page 500. While the first three books are completely hilarious and preposterous and just down right silly, the last two books take a more somber look at the people who have to deal with this infinite silliness as an everyday reality. Like, you wouldn't want a clown showing you magic tricks on the same day that both your parents died in a car wreck. You just wouldn't be in the mood. That's sort of what the universe does to these characters. It never stops joking, it never starts being easier to understand, it's just a completely overwhelmingly horrifyingly enormous and complicated thing that basically just wrecks your life at every possible turn.
I feel that the basic message is that, while there is a universe, and maybe other universes, and an infinite amount of everything, it is more important to focus on your own personal universe and the perceptions and memories and realities that are true to you, not true in the big scheme, because you will never actually truly understand that.
Most importantly: Don't Panic.