As of 2026, Susskind has hinted at a fifth volume ( Quantum Field Theory ) and a potential of General Relativity if new discoveries (e.g., quantum gravity phenomenology or gravitational wave memory effects) become standard knowledge.
The theoretical minimum culminates in the "action" principle. Just as Newton gave us $F=ma$, Einstein gave us the relationship between geometry and matter. the theoretical minimum general relativity pdf upd
The series includes: