A sixth installment in the Hitchhiker's Guide series. Sadly, not written by Douglas Adams, which means this is either going to be a respectful continuation of the series by someone who's got a good handle on Adams' writing style — like the continued radio plays were — or it could just be fanfic. Not that I have anything against fanfic, but I don't usually expect to pay for it (Grantville Gazette excepted), and this is not a shining example of the genre.
On the upside: there are some good ideas here that could have made for an interesting Hitchhiker's story. On the downside: I found very little of it funny, which meant that I was much less willing to forgive it having nothing resembling a coherent plot, and I don't think Colfer really managed to nail the "voices" of any of the characters (with Ford and Zaphod being particularly bad). Other things that grated: none of the new names sound convincingly Adamsish; reusing the "Ford Prefect" joke ("Hillman Hunter") is just lazy; it wasn't necessary to namecheck every species and character previously mentioned in the books. (I was a bit surprised that he didn't find an excuse to bring Marvin or Eddie back, though.)
So, sorry — avoid this one. I don't think I'm likely to be picking up any of Colfer's other books any time soon either.