Alright, diving into books about Death personified as a character? I'd actually recommend 'Mort' by Terry Pratchett. Don't let the Discworld series intimidate you; this one stands alone brilliantly as a starting point.
It's not a grim, horror-filled thing at all—it's a comedic fantasy where a teenager named Mort becomes Death's apprentice. The tone is witty and surprisingly philosophical, asking big questions about life and purpose without ever feeling heavy. You get a Death who's fascinated by humanity, collects cats, and tries to understand us. It completely subverts the scary skeleton trope.
For a beginner, it's accessible, relatively short, and it hooks you with humor before the deeper themes sneak in. The character work is so good you end up rooting for Death himself. After this, if you want something darker, you can always branch out to Neil Gaiman or others.
It's basically a perfect gateway.