The Ultimate Hitchhiker's Guide 
This omnibus edition begins with The Hitchhiker's Guide to the Galaxy, in which Arthur Dent is introduced to the galaxy at large when he is rescued by an alien friend seconds before Earth's destruction. Then in The Restaurant at the End of the Universe, Arthur and his new friends travel to the end of time and discover the true reason for Earth's existence. In Life, the Universe, and Everything, the gang goes on a mission to save the entire universe. So Long, and Thanks for All the Fish recounts how Arthur finds true love and "God's Final Message to His Creation." Finally, Mostly Harmless is the story of Arthur's continuing search for home, in which he instead encounters his estranged daughter, who is on her own quest. There's also a bonus short story, "Young Zaphod Plays It Safe," more of a vignette than a full story, which wraps up this completist's package of the Don't Panic chronicles. As the series progresses, its wackier elements diminish, but the satire of human life and foibles is ever present. --Brooks Peck
Reviews
1) There is little to no narrative drive. Adams intrigues the reader with some interesting narrative points early on, but never actually gets to finishing the point, leaving the reader wondering why there is no resolution (was he bored when he wrote? or is he just sloppy? probably the latter).
2) There is little cohesion to bind the five part trilogy together. It's really just one random story after another. In fact,it's not really a story--it's more an extended TV series in which the writers make up plot points as they write (a la Alias). Sloppy, sloppy, sloppy.
3) Only the first book seems to be truly good. After that, it goes downhill. Unfortunately, the first book, ending without a conclusion such as it is, only makes the reader want to read further, which upon completion of reading further,the reader becomes disappointed that the further reading was not as good as the initial reading, which in turn makes the initial reading not as good as initially thought. Conclusion: overrated series.
It is however, somewhat funny. Hence, the two stars.