Sorry for having to state the obvious here: This is not a book by Douglas Adams.
The main difference is that Douglas wrote SF with a portion of (wonderful) humor, while Eoin Colfer has written a comedy with SF elements. Still a really entertaining read, and the many references to the other Hitchhiker books made me feel all warm and fuzzy inside, so much that the fourth star is for merely sentimental reasons.

The last book in the series will now be "Don't Panic: The Official Hitchhiker's Guide to the Galaxy Companion" by Neil Gaiman.

This is the last book in the Hitchhiker Trilogy pentalogy, and it was supposed to be a bad book, according to several reviews that I read. It was even described as depressing, not worth the read and that one would be better off by reading So Long, and Thanks for All the Fish as the final installment and then stop, in order to keep the series in good memory.

I shouldn’t have listened to those reviews, because saying that this book was bleak or even sad is utter BS. Granted, the undertone may be a bit less cheerful than in the other books, but nevertheless the story is brimful with the crazy funny stuff I adore Douglas Adams for.

Here are some examples – without spoilers or further explanation – to pique your interest, if you have refrained from reading the last Hitchhiker book until now:

• a Grebulon ship tries to find out why its system does not work properly
• Tricia realizes that there are actually two rules about going back for your bag
• the Hering Sandwich experiments
• the anti-Marvin
• the welcoming planet of NowWhat

All of these examples are only from the first eighty pages; I stopped taking notes afterwards. So stop giving me that “Oh, he had a bad year when he wrote it” stuff. I know, Douglas said so himself, but still!

If you can’t see the loads of humor in this book, then, dear reviewer, you’re a Vogon.