Terry said you can start anywhere, and I’ve been enjoying reading them in order, but if you want to get to know the Death character, “Mort” and then “The Reaper Man” would do. The witches and wizards books are also great, and he’s in every book at least a bit (he is Death after all).
I might be parasocially in love with Death. He’s just such a dear, kind, awkward but in a stoic way, person. And he loves cats 😻
The new recordings that are coming out on Audible are FANTASTIC if you like audio books at all. There are two versions, the newer ones with Peter Serafinowicz and Bill Nighy are the good ones.