For those that don't know, And Another Thing... is the 6th book in the Hitchhiker's Guide to the Galaxy series that was written after the death of Douglas Adams.
At first I was a little put off reading it because it felt as if I was reading fan fiction(which I suppose it technically is) due to the style not quite meshing with that of the original books. It also felt like it was written for a younger audience which I guess is somewhat understandable given that the author has mostly written books for young adults. There were a few other minor things that annoyed me such as the use of abbreviations and nicknames that were never used in the original books. An example of this is that pan galactic gargle blasters were often shortened to just gargle blasters.
However, the book seemed to get much better after the third chapter as far as style and reading level goes and the annoying abbreviations/nicknames were also much reduced in frequency. So I'd say that overall I rather enjoyed the book and gave it a 4 star rating, though I was quite disappointed that Marvin did not make an appearance in this story.
I would definitely recommend this book to those that are fans of the original five books especially since this one has a much less bleak ending than Mostly Harmless. As a side note, I am glad I decided to read The Salmon of Doubt before I read this book as it helped me to get a joke made regarding something that happened in the childhood of Douglas Adams. It's a rather minor thing though and it is by no means necessary to read The Salmon of Doubt before And Another Thing...