I’ve only read two non-Discworld novels by Terry Pratchett, and this is one of them. Probably an ex-library book, though I forget where I bought it.
Young Johnny Maxwell is importuned by the dead in his local cemetery when they discover it’s going to be redeveloped. This is a novel for young adults about friendship and tradition. Johnny has to convince his friends and get them on side, so they can help scare the shit out of the developers. The ghosts, who get pretty active when they’re riled, do most of the heavy lifting in this regard. They’re the tradition part, a past come to life that informs the present in a very direct way.
A lovely, funny story, particularly in Johnny’s growing friendship and respect for the ghosts. There is an earlier Johnny Maxwell novel, Only You Can Save Mankind, which I haven’t read yet. I’m keeping an eye out for it.