So hitchhikers guide I can certainly agree with, but the rest of the series is pretty inconsistent. Restaurant was pretty terrible in my opinion, but then Life is almost as good as the original. I'd say the quality of the series is downhill from there. The follow up books didn't introduce many interesting situations or ideas that weren't already presented and so it just felt like it was dragging on.
I like So Long and Thanks for all the Fish, in part because of how sweet and optimistic it was. After finishing I then was shocked by how dark and depressing Mostly Harmless was.
One of the greater modern literary tragedies is the way Adam's said he wrote Mostly Harmless when he was in a very bad place mentally. He said he intended to write a followup to cap the series off in a lighter way but then died before he was able to.
