Well, I have to admit that I have a bit of reluctance to read this book. If it is not for group read, I might have skipped it entirely. The reason is: The movie sucks!
So, I read it. It is pretty much better than the movie. It looks like that it is not easy to transfer a radio show into a good movie, but it is easier to transfer it to a book. I am still looking for the original radio transcript.
There are no obvious story line in this book, except that you follow two hitchhikers from Earth (one Earthling and one alien). The story is a satire, laughing at our daily life in a hilarious beyond Earth setting, with not-quite-intelligent alien life forms (in form of humanoids, reptiloids, and all other-loids), with exception of Zooey Deschanel.
There are plenty of English dark humor here that give me quite a laugh, but unfortunately not enough story line to get me hooked. I cannot help to compare it with Redshirts, with has better plot therefore much more enjoyable. I am not going to spoil the humor in this review, so read it by yourself. I also find that the first half of the book is funnier that the rest. So many clever jokes, especially when you can get out of your Earth-view, and laugh at those ignorant Earthlings (a.k.a carbon based oxygen sucker semi-intelligent life form).
So, the final verdict: read the book (or better get the original radio show), but avoid the movie like a plague.