This is one of my favorite Pratchett novels. His work is always about the question of how to be human, which in this case means the relationship between our past and present, the dead and the living.
His ability to imbue even a brief sketch of a character with life, humanity, and of course humor is on full display–we are very funny creatures, after all–along with his fundamental optimism. Without ever being leaden about it, the difference in perspective on modern life between the dead and living characters in this story makes clear how what we think depends on where we’re looking from.