D+ for "Good Omens" by Neil Gaiman and Terry Pratchett
I started reading it, then I started enjoying it, and then stuff happened, the story jumped around, and then more stuff happened. Then I started to get bored. Some of the jokes were good and all, but it was a bit too jumpy for me. In the end, I finished it only because I'd gone so far and the weight of positive reviews that had been posted urged me onwards.
Hal Spacejock is funnier, as is Heinlein's "Job: A comedy of justice" (among others)