Hi Matt,
I recently picked up "Designing Movie Creatures and Characters : Behind the scenes with the movie masters"
It covers individual fx companies such as ADI, KNB, concept artists like Steve Wang and Suit performers like Brian Steele.
But there's also great sections called the Art Of Making Molds, Monster Materials and The Science of Appliance... perfect for sculpt, mold and casting tips
Another great book is Monster Makers Handbook which is essential a how to from start to finish of making masks