I wish he'd carried on with sf in some ways, it needs a poke in much the way that the fantasy genre did before Diskworld. I've been reading a lot of first novels recently and they are often wobbly. Pratchett displays a few tiny wobbles here but you definitely get a sense of impending master from his humour, timing and characters.
I somehow missed reading this when it came out all those years back. I'm very glad I read it now.