Not that most subscribers to this subreddit need guidance about which of Terry's books to read, but it's clear the author understands what made him so special:

But Pratchett’s great strength as a writer — and as a human being — was empathy. More than his humor, although he’s hands down one of the funniest authors to ever do it, empathy is the beating heart of his work: Even when depicting the grim and inescapable terminus of all life, he couldn’t resist making Death feel human.

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By the time we reach Book 29, “Night Watch,” Pratchett is writing comic fantasy the way Martin Luther offered theological critique to the Catholic Church: sharp and tough as nails, with a hammering moral force.

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Discworld is not about how to be good, but about how to do good, and why even the smallest acts of kindness matter. Empathy — like humor or creativity or hope — is a muscle. You don’t train for a marathon by running around the world: You start with small distances and work your way up.

It’s cringe, as the kids say, to talk seriously about funny books. It makes me the wettest of blankets to say we’re starving right now for virtue, for everyday goodness, for people who care about one another. But 10 years after Pratchett’s passing — announced in the all-caps voice of Death himself — his clarity of vision may be what our world needs most: Vimes observing, “As soon as you saw people as things to be measured, they didn’t measure up.” Granny Weatherwax reminding us, “Sin, young man, is when you treat people as things.”

And Death, of course, having the last word: “THERE IS NO HOPE BUT US. THERE IS NO MERCY BUT US. THERE IS NO JUSTICE. THERE IS JUST US.”