In the fifth, and final, book of the Hitchhiker trilogy Adams leaves the reader feeling satisfied, but at the same time rather empty. Plot never being a key factor in Adams' novels, Mostly Harmless carries on the trend in fine style. Not that this has a major effect on the enjoyment of the book, but it can be at times a little confusing.
A promising mysterious start pales into insignificance as the book progresses and the introduction of the unknown ship is bordering on irrelevance. A few chapters into the book we are reintroduced to Arthur Dent and Ford Prefect but any others characters seem to have only a small role to play or have been completely forgotten.
Although the ending is wrapped up nicely a few major issues are left unresolved, such as the disappearance of Fenchurch and the whereabouts of Zaphod, but the clean wit and the unrivalled ability to make any situation seem interesting or obscure hold the book together well and overall make the book an enjoyable read. Interestingly the book is fully summed up the character Random and the title Mostly Harmless.
I would say a book for the more dedicated fans, who maybe appreciate the writing style more than any kind of structure or plot, but sure to make you laugh at some point otherwise.