You should read it.
I had not read it for quite a while, on the impression that it was a sixth Hitchhiker's Guide sequel worked up by another author from scrounged notes. It is not. What it is is infinitely better than that, and far more wonderful. I found the process of discovering what it was to be deeply interesting and enjoyable, and I don't want to spoil that for other people who I know will click through "spoiler warning" cut tags, so for now I am leaving this cryptic note and writing up a review to post in a few weeks once I've pressed the book on several appropriate handy people.
(Also, some of this is selfish; I am very curious whether the relevant handy people will have similar experiences of it to mine without my prompting.)
 It appears that there is a book of that description, though, without so much as scrounged notes; perhaps I was confusing it with that.