Also, to be clear, I haven't worked through most of Sussman, so I can't recommend it one way or the other. I was just commenting on the handling of the Legendre transform.
Later I tried to learn Quantum Mechanics while taking a course on Operator Theory, but gave up on using Volume 3 of Livshitz-Landau because it was just too impenetrable. I ended up going with Sakurai instead.
I found Volume 1 to be beautiful read and felt like I was learning something profound. Volume 3 was beyond me. The only thing I'd say these books have in common with the Feynman Lectures is a dearth of exercises. This wasn't an issue for me reading Volume 1 of LL because that Calculus of Variations course had many exercises which I just wasn't in a position to appreciate without knowing more Physics.
