@LoliOwar of course Sorry in advance for the small essay
Death appears in quite a few, as the main character it might have been Mort or Reaper Man. Both good reads, both can be read alone(I’ve just finished Reaper Man for the Nth time)
I suspect you’d remember less Death and more Susan / other themes if it had been Soul Music, Hogfather, or Thief of Time.
You could give Witches Abroad a go. It’s one of the witches books, pretty fast paced, can be read in a little over a day. Themes include fairy tales, fairy godmothers, voodoo, carnival, narrative causality etc The story gives you a great introduction to the witches, what they’re like and what drives them, while also being mostly light hearted and playing with a bunch of tropes.
Another option would be Going Postal. More steady pace than Witches Abroad and lead by one of the most cheeky/charismatic characters in discworld. Moist is charged with brining back the possibly cursed Postal Service and all the challenges there in. Themes include corporate shenanigans(both good and bad), modernisation, human rights, the Gods, hope and redemption.
Both can be read as standalone books. If you like the characters, Witches Abroad is the 3rd book in the witches story arc and there are plenty that follow on from it.
I wouldn’t stress about going back, there is some bits of background they add to some of the characters, but its not essential I would however recommend reading the Witches books in order from here.
Going Postal is the first of the Moist Von Lipwig books and has also been made into TV/Film by Sky, it was an ok adaptation.
One last one, if you like crime fiction, Guards Guards, first of the City Watch story arc. This arc, I think, has the greatest character progression, so I would recommend reading these in order. Each story is has elements of your typical police novel, but Pratchett doesn’t skip the grit. He tackles serious personal and systemic problems with humour wit and satire. On the surface they a good fun romp around the city and occasionally the Discworld, but there is a lot in these and I’m still picking up details and philosophies having read them over and over and over.