Fundamentals of Materials
None, actually! But you should take 3.091 beforehand.
The Structure of Materials by Allen & Thomas - Very useful, the structure lectures often follow the book.
Thermodynamics in Materials Science by DeHoff - Not as useful, but necessary. All in all, the thermo book is a good reference.
3.012 is split into two sections, structure and thermodynamics. As a result, it's often co-taught, which can be good or bad. It has no final exam, but one test for each section - definitely helpful for finals week. Psets are somewhat short and have medium difficulty.
If you know what you're doing, 3.012 is very passable. Just don't fall asleep during the two hour lecture period.