How difficult is STATISTICAL MECHANICS, a physics graduate level course?
A graduate level course in QM is usually prerequisite to graduate level stat mech. They’ll assume, for example, that you are intimately familiar with all the quantum energy levels available to a particle in a gas or a particle-in-a-box or a harmonic oscillator or a spin-1/2 system. If those terms vaguely ring a bell for you, you should review them before starting. If you haven’t heard of them, don’t bother with stat mech–go back and take quantum. Also, it is good (if not absolutely necessary) to have had an undergraduate stat mech course. The graduate course starts from the beginning, but moves very quickly through material most students will already have seen as undergrads.