Mort is a good place to start - I think it's the first of the books that focus on the anthropomorphic Death.
I'm fond of Guards! Guards! too, which is the start of the Night Watch stories, which are my favourite of the strands that run through the series. In a city where crime has been legalised (and given quotas - the city's dictator is delightfully Machiavellian), the Night Watch is a defunct organisation, staffed by imbeciles and run by a jaded if capable alcoholic. The boss is always depicted in the cover art as a sort of Clint Eastwood type - possibly in reaction to the watch motto - Fabricas Diem, Pvnk. Their idealistic new recruit may be the rightful heir to the throne, and there's a plot to overthrow the dictator and install someone worse. Pratchett wrote it after thinking about the guys they always yelled for in the old movies - "Guards! Guards!"
Of the relatively stand-alone books, I adored Thief of Time. Just to give you a flavour, the lead character is a monk who practices "deja fu", which is a martial art that leaves one with the impression that one has been kicked in the head that way before. His order seems to be modelled on the Buddhists, but they worship, protect, and manipulate time. In spite of that, he derives his philosophy in life from the aphorisms of his old landlady, which he has collected in a little notebook. Lines like, "If you keep picking at that, it'll never heal" are treated with reverence. It's simultaneously sweet and funny, and a great send-up of religion. It's a fun adventure too.
Last edited by mikhail; 27-03-2020 at 22:04.