There is nothing quite like Pratchett, but I second the thought of Piers Anthony, and his less flippant "Sos the Rope" series is well visualised. For fun and phony(ish) magic, you could try The Myth Adventures by Robert Asprin (later novels in the series with Jody Lynn Nye). For fun and sharp political observance, try Keith Laumer's "Retief of the CDT" series. Also with politics, magic, and humour there is Christopher Stasheff's "Warlock in Spite of Himself" series.

If you are an SF/fantasy reader you have of course done Tolkein. You should also try the Chronicles of Thomas Covenant the Unbeliever. No longer current, but a foundational author you should have read is Asimov, particularly the Foundation series. Some of CJ Cherryh is worth a look.

Other thoughts may occur to me as I walk by my bookshelves...