#1 The Hitchhiker’s Guide To The Galaxy: Is This An Overview? 

Arthur Dent’s home is about to be demolished for a bypass because the planning council did not properly inform Arthur of their plans.  What the demolishing crew, Arthur, and the all the humans of Earth did not know, is that Earth was going to be demolished to make way for a hyperspatial express route as the galactic council did not properly inform anyone on Earth. 

Fortunately for Arthur and unbeknownst to Arthur, Arthur’s friend Ford Prefect is not actually a human.  But an alien who has been stranded on Earth.  Ford saves Arthur by hitchhiking on a demolition spaceship.  A spaceship composed of a Vogon crew, who are not friendly to hitchhikers.  Resistance is futile.  

Somewhere else in the galaxy, the reveal of the new spaceship containing the Infinite Improbability Drive is being stolen by the President of the Galaxy Zaphod Beeblebrox, along with a companion, Trillian.  Zaphod is searching for the legendary planet of Magrathea, a planet that build custom-made luxury planets for the extremely rich during a former Galactic Empire.  Magrathea was so successful that the rest of the Galaxy became abjectly poor.  Against all improbability, Arthur, Ford, Zaphod, Trillian, and a manically depressed robot called Marvin, hitchhike across the galaxy.  Don’t Panic.  

Caveats? 

This book blends science fiction and comedy to create something improbable.  Sometimes prioritizing one or the other, to create a series of meaningless coincidences, but a meaningful adventure across the galaxy.  There are parts in the book that are inconsistent given the information provided before, which is acceptable given that the inconsistencies were meant to be there.  

#2 The Restaurant at the End of the Universe: Is This An Overview? 

Don’t Panic, as the spaceship Heart of Gold is being attacked by Vogons and the hitchhikers cannot get the computer to think about escape options.  The computer has its bandwidth preoccupied with trying to figure out how to give Arthur the requested cup of tea, that actually tastes like tea.  All this excitement, and all Arthur, Ford, Zaphod, and Trillian wanted was to get food at The Restaurant at the End of the Universe.  As the computer is preoccupied, the escape plan was to have a séance.  A séance in which Zaphod learned the reason why Zaphod stole the Heart of Gold, to find the person who rules the universe. 

Through some improbable situations, the hitchhikers actually find their way to The Restaurant at the End of the Universe.  So named because the restaurant exists, or is going to exist, or did exist in a time bubble and projected forward in time to the End of the Universe.  Guests enjoy meals while watching creation itself explode around them.  

To avoid a series of improbable events, the hitchhikers steal another ship, and are sent on a journey of another series of improbable events.  Unbeknownst to most of the them, the ship is apparently bound by autopilot to sundive, as in dive into a sun.  While these events are happening, Arthur is reminded to figure out the question to the answer of 42.  And then there is the android Marvin, who everyone ignores because its Marvin. 

Caveats? 
Not all the comedy is for everyone.  Especially as human culture changed. 

As the events can change locations quickly for purposeful improbable reasons, there is often early confusion as to where the characters are. 

#3 Life, the Universe and Everything: Is This An Overview? 
What does Marvin’s leg, the Infinite Improbability Drive, a plastic scepter, an artistic award, and ashes from a trophy have to do with saving the universe?  Slartibartfast will have to tell Arthur that after Arthur finds a way to escape prehistoric Earth.  To help, Arthur would also need to escape a very angry alien, who is angry at Arthur.  Arthur has apparently been innocently and coincidentally murdering the same alien throughout Arthur’s hitchhiking across time and space.  

Arthur seems to be the only one who listens to what Slartibartfast has to say, because the others have their own preoccupations.  At the prospect of the end of the universe, all Ford wants is to spend the last days in bliss.  Zaphod is dealing with the trauma of having fulfilled one’s purpose in life.  Trillian could not stand Zaphod’s behavior, and left to a random location in the galaxy.  Marvin has been going around in circles.  A couch stalks the hitchhikers.  What is the cause of the end of the universe?  

Caveats? 
The comedy and the characters are consistent with the prior books in the series.  With minor character development.  What the reader thought of the comedy and characters before, is not likely to change. 

#4 So Long, and Thanks for All the Fish: Is This An Overview? 
After hitchhiking across the galaxy, Arthur is no longer culturally shocked to what the universe thinks.  Arthur is completely bewildered by the fact that the Earth exists, therefore Arthur does not panic.  Apparently, there was a global hallucination of large yellow spaceships.  There appears to be only one other person, Fenchurch, who knows that the Earth has been destroyed, but those ideas make Fenchurch seem mentally unfit.  As Arthur can validate the ideas, Arthur falls in love, only to lose Fenchurch’s phone number. 

While Arthur is not being puzzled by the existence of the Earth, Ford has been waiting for the next edition of The Hitchhiker’s Guide To The Galaxy to update and remove years of Ford’s work on the Earth entry due to the nonexistence of the planet.  Ford is surprised by the update, as rather than removing the two words about the Earth, find that the entry has expanded.   As Ford is hitchhiking across the galaxy to inform Arthur that Earth exists, Arthur and Fenchurch seek to find what happened to the missing dolphins.  Apparently, the dolphins knew something about Earth.  

Caveats? 
This book follows mostly Arthur’s adventures on Earth.  

#5 Young Zaphod Plays It Safe: Is This An Overview?
Before Zaphod became President of the Galaxy, Zaphod was part of a salvage operation.  Apparently a spaceship that could not crash, crashed in an ocean trying to obtain the best lobster.  Everything is perfectly secure, perfectly safe aboard the crashed ship that contains various hazards that could harm a planet.  What the group was trying to salvage was something more dangerous.  A by-product, of some sort.  The officials who know the safety procedures, do not care if Zaphod knows what the crashed ship contained, because nobody would believe Zaphod. 

Caveats? 
This is a very short story, which adds context to the different improbable events which effected a planet somewhere in the galaxy. 

#6 Mostly Harmless: Is This An Overview? 
Arthur has already had misadventures in hitchhiking across space, and across time.  This misadventure has Arthur hitchhiking across parallel universes.  Which take from Arthur all that Arthur wanted, the Earth and the person Arthur loved.  At a loss for a life, Arthur hitchhiked to a planet whose inhabitants provide wisdom.  Wisdom that Arthur ignores.  After disapproving a version of an Earth, Arthur becomes a professional hitchhiker, only to crash and become stranded on a planet.  At least Arthur meets Arthur’s daughter.  Not that Arthur knew that Arthur had a daughter. 

While Arthur is dealing with the loss, and gain, but mostly loss, Ford is stealthily trying to gain access to The Hitchhiker’s Guide To The Galaxy publishing offices.  The stealth attempt is not going exactly to plan, because the offices are slightly different.  Every time the guide moves, the offices are meant to be reconstructed in the exact same way.  Turns out that the guide has new owners, who Ford does not appreciate.  Ford finds out what the new business plan is for the guide, and immediately understands the danger.  After an escape and theft, Ford hitchhikes to Arthur.  All these events are not improbable, as the events were arranged to make them happen.   

Caveats? 

All the events that seem to be random, are actually somehow not random at all.  Some parts of the book seem to be purposely confusing, until a later explanation.