One SFSignal review gives it 3 out of 5 stars, saying,
The Light Fantastic is a true novel-length story. Sadly, that story does not take a whole novel to tell. The result is a fair number of times when the book seemed to plod along too slowly despite the humor.while a different reviewer at that site gives it 4 1/2 out of 5 stars calling it "a very strong Discworld novel".
There is a section of the author's site devoted to the series. The wiki devoted to Pratchett in general and Discworld in particular has lots of information.