Not really countering the point I was making... I agree that monsters do play a part and are indeed the focal point of the scenes they are in, but in general these scenes play second fiddle to the others where interaction with intelligent races is the main score. Heck, half of the encounters with monsters come from the earlier interactions with inteligentia... The Rancor? Jabba's pet. The Sarlac? Jabba's execution toy. The Nexus? Entertainment on Geonosis. Etc. Etc. They aren't a big focal point of the movies in my opinion and I cannot make a list long enough to fill even half a book if we would stick to the 6 movies we have (even if we included mounts and beasts of burden.)
Sure they play second fiddle to the main story - it's called Star Wars and not Beast Riders of Tatooine, after all - but I'd say that they're still pretty important given that most of the Monster Encounters add nothing to their respective stories, other than go "Look! It's a monster!". Big fishes on Naboo? Could have been easily cut. Wampa? Really just an excuse to cover up Mark's car crash scars. Snake Thing that Eats R2 on Dagobah? Nothing but a bit of slapstick for our droid. All they do, is demonstrate "Hey, this is a pretty diverse universe" and reinforce the Flash Gordon-y nature of the setting.
As for filling the book, sure we'd only get a couple of pages out of the movies. No reason why there couldn't be more FFG generated material around that same theme.