I've listened to a ton of them as audiobooks - there are some fantastic performances out there.

Thud was my first, and remains my favourite.

I'm a big fan of stories involving Ankh-Morpork, especially the City Watch. Sam Vimes is my homeboy. Sergeant Angua is adorable. Moist von Lipwig is endlessly enteraining.

I've enjoyed all the novels I've experienced to date, though I found the witches increasingly repetitive and tedious. Furthermore, Rincewind can suck it.