The plot in a nutshell
The film is based on the very well known and quite popular books by Douglas Adams.  Actually, it's based on the first book of his five part trilogy.

Arthur Dent awakes one day to learn that his best friend, Ford Prefect, is not what he thought, and that the Earth will be destroyed to make way for a hyperspace bypass.  And if you're not interested in getting involved with local politics, well, the Vogons have little sympathy.

Arthur is then on a whirlwind space adventure with Ford, his lost love Trish McMillan, the president of the Galaxy, Zaphod Beeblebrox, and Marvin, the extremely depressed robot.

So far, many of the reviews I've read for the Guide remind me very much of this scenario.  Now, don't get me wrong - this adaptation of the Guide is NOTHING in comparison to the amazing work that FOTR was.  But it's not the steaming pile of nasty brown stuff that so many people are claiming.  Of course every line of dialog from the book isn't here, since every novel is longer than a screenplay.  To adapt a book requires the gleaning of the most important parts, to weave the critical story, while leaving out the extraneous niceties.

This adaptation isn't perfect by any means.  There's some poorly handled story devices, including the explanation of Zaphod's unusual anatomy.  There's some lack of definition around what's really happening or why, but that's not all that surprising.  The books were not intended to be deep, wise, compelling stories.  They were wonderful dialog written with witty, dry humor and lots of satire on the human condition.  Some of that managed to make it to the film, and some of it didn't.

The problem with dry humor is that it often translates to film poorly.  The British series The Office is a wonderful example, and while it was lauded as a great comedy, it was not done so by the majority.  Most people would find it rather dull, or simply not their cup of tea.  Or something that approximates tea, but isn't quite.  The American version attempted to get a little more over the top and still have a lot of the dry, wry sense of humor, but only time will tell if it plays to the masses.

Reading this kind of humor works great - watching it played out often does not.  There are some truly funny moments in this film however (my favorite was the whale's thoughts as he headed for the ground), and many of these revolve around the narration.  Using the narration was a key point to making this film work, since most of the best bits were buried in the Guide itself.  However, there are some wonderful exchanges of dialog missing from the film that most fans of the book will sorely miss.

The screenplay was started by Douglas Adams, but his untimely death meant that another writer had to finish it.  It's tough to say how close this was to his vision, but I'll give them the benefit of the doubt.  Oddly enough, in an adaptation of a book with tons of witty dialog, it's the acting that saves this film.  Almost every character was extremely well cast, from Martin Freeman (from the aforementioned Office) as Arthur Dent, to Zooey Deschanel as the lovely Trish.  Zooey was particularly good in the early scenes at the party, and then again later around the Point of View gun.  Actually, all the actors did their best work in the quiet moments, when the dialog was allowed to have a little greater control.

My only disappointment was with Sam Rockwell as Zaphod.  Perhaps it was the wonky way they handled his physical abnormality, perhaps it was his over the top presentation, but either way, he never worked for me, especially among the other characters.  The seemed to have more depth, whereas he remained a caricature throughout.

The surprise standout was Mos Def as Ford Prefect.  I knew that Allan Rickman (Marvin) and Freeman were perfect casting, but I was still unsure about Def.  But although he didn't sound, act or look like I ever expected Ford to sound, act or look, he managed to make Ford real.

There were lots of roadblocks that this film had to maneuver to make it to great - a very devoted fan following that knows the book by heart, a dry, satirical style that is difficult to translate to film, and the use of many of its jokes and ideas in other films already since it was written over 25 years ago.  Many of the people that see the film in its opening weekend will already know what's coming - there will be no surprises for them.  They'll see it with a far more critical eye than the the rest of the galaxy, and that will make it tough for the movie to get a good word of mouth going.

If this film was not an adaptation of a book, it would do much better, but as an adaptation it's going to get slapped about the head and face fairly hard. This won't be on anyone's top ten, but I suspect that over time it will be recognized as a better film than it will be initially.  Given a little time, and a little distance from the book, and it will fare much better.

Rating - A guarded Wait for the Rental.
The humor in this film will play out just as well on the small screen as the large, but there are some interesting visuals that will make seeing it on the big screen a little more enjoyable.  For example, the scenes in which Arthur visit's the floor of the factory 30 feet of screen to be really appreciated. 

Most people can save a few bucks though and wait to pick this up at the local video store.  And for those interested, I'll be picking up the toys (including the 10" Marvin) over the next week for reviews!

Spoiler Laden Thoughts
I won't spoil anything here, but if you have read the book, don't expect too many surprises.