I am reading the Discworld novels in published order, and, for me, this is probably the weakest so far. It is still very readable, with a clear narrative, lots of tangential musings, and some very funny lines. It just didn't grab me as much as the others I have read so far. The story centres on the appearance of a sourcerer at the Unseen University, and the consequences, with Rincewind - an old friend - seemingly the only one who can save Discworld. He picks up a couple of fellow travellers along the way, before the final denouement. The story moves along at the author's usual rapid pace, but once or twice, particularly at the end, characters inexplicably change just to make the story work, which I found rather spoilt it for me.