Edition: Corgi, 1991
Review number: 32
I think this is probably my least favourite of all the Discworld novels. Reading it again, I found that I did pick up more of the film references than I did the first time around (the benefits of several more years of film-watching).
Briefly, the plot is that the idea of movies invades the Discworld, sending people mad in ways that mimic various Hollywood characters - Sam Goldwyn, Charlie Chaplin, Rudolph Valentino and so on. There's even a (dumb) super-dog called Laddie. The hole this has made in reality is, of course, ready to be taken advantage of by horrendous monsters, and it is up to the hero, an apprentice wizard turned film star, to save the world singlehanded.
The best joke in the book is the animals who, affected by the magic near the holes in reality, start to talk; they insist on being called things like "Definitely not Sweetums" and "Don't call me cute". Generally, though, the multiple film references are far better done by authors like Tom Holt and Craig Shaw Gardner; it's a Discworld novel for completists only.