"We don't know where we're going, she thought. The only important thing is to go. Masklin was right. This isn't our world.
"'Perhaps we should have talked to the humans,' she said aloud.
"'No, you were right,' said Dorcas. 'In this world everything belongs to the humans and we would belong to them, too. There wouldn't be any room for us to be us.'"
"Diggers" is the delightful continuation to the trilogy begun by "Truckers." As you would expect from a Pratchett book, there's plenty of zaniness action, with the final action sequence featuring a bunch of tiny gnomes trying to escape from human predation by making off in a JCB (a front-end loader) they've named Jekub. It's silly, it's over the top, and it's also a meditation on sapience, self-awareness, and, for lack of a better word, the human spirit. Maybe "perseverance" would be more appropriate. Anyway, it's about how the Nomes are aware of the humans, but the humans are not aware of the Nomes, and would destroy their habitat and enslave them if they could. In response, the Nomes have to fight back.
Pratchett always had an uneasy relationship with the non-human world, and the whole problem of Other consciousnesses. He often featured Other humans, non-humans with human-esque consciousnesses, and machines that took on some of the features of consciousness or life, and was fascinated both with the creative possibilities such stories offered, and the moral/ethical issues they raised. Interestingly, if somewhat depressingly, he was in general more empathetic and interested in the non-human earlier in his career, and "Diggers" is one of the high points in his fascination with the Other that is still us.
But don't let that deter you from reading what is basically a middle grade fantasy book. "Diggers" is short, funny, and easy to follow, and the philosophy is easily disguised as just more action. Not the Discworld, but very worth reading even so.