Weinberg: Gravitation and Cosmology - The definite reference Padmanabhan: Gravitation: Foundations and Frontiers - A modern point of view Feynman: Lectures on

Weinberg: Gravitation and Cosmology - The definite reference Padmanabhan: Gravitation: Foundations and Frontiers - A modern point of view Feynman: Lectures on Gravitation - Feynmans unique insights are a rare gem Mukhanov: Introduction to Quantum Effects in Gravity - The best introduction to quantum gravity (and also quantum field theory)