Although they are all pretty silly, there are a few standalone Discworld books with more of a serious plot and typical fantasy characters. My favorite is probably "Small Gods", which is based around the idea that Gods as real beings exist because of their believers, rather than the other way around (sort of like in American Gods_. It focuses on a random young acolyte of the local cult, who has accidentally become the last remaining true believer. Another good one is "The Monstrous Regiment": a young girl escapes from a Dickensian boarding school, dresses up as a boy, and joins the army. Unfortunately, her assigned unit it full of mysteries and alarming characters who she needs to deal with before she can rescue her vanished brother.