Ballentine is excellent, but it should be your third book on QM, not your first. Griffiths and Isham are good choices for the first two books. However, if you want want to see every relevant theorem stated and proved, you need to study some measure/integration theory and then functional analysis (e.g. Kreyszig or Sunder). After that, I suggest Strocchi.
Classical Mechanics
Introductory: Mechanics: From Newton's Laws to Deterministic Chaos-Scheck
More advanced: Introduction to Mechanics and Symmetry- J.E. Marsden Foundations of Mechanics- J.E. Marsden
Quantum Mechanics
Ballentine, as others mentioned Introductory Quantum Mechanics-Liboff Mathematical Foundations of Quantum Mechanics-Neumann
EDIT: Liboff is considered an introductory text but a much superior one than, let's say, Griffiths.