This is the final book in the "Hitchhiker's Guide" set. As you can see from the stars (or perhaps you can't if you have Lynx, or a very short term memory), I didn't like this book at all as much as the first series.
I can't very much explain the reason why, except perhaps to say that Douglas Adams was in a very different mood when he wrote it, and I when I read it. The style of writing is the same, but many of the situations are somehow more stressed, with less light-laughability. There seemed to be a destination firmly in view, as opposed to the first four books which seemed to flow wherever they desired. This is probably a result of the author wanting to end the series for certain, since the ending of book #4 left some small things hanging. To be sure, there are several parts which take up the pointless, odd, but brilliant humour that so characterized the first volumes. A being intent on the destruction of Arthur Dent is my favourite.
I guess the thing I didn't like was ending, which I'll leave as a surprise(?) to anyone who feels the need to read this book simply because it follows their favourite trilogy. I'll always like the first four, which are included in my omnibus edition, but I don't think I'll read this particular book again too soon, as it is slightly depressing for a humourous novel.