Mastering the three volumes of Steven Weinberg's "The Quantum Theory of Fields" would certainly provide you with a strong foundation in quantum field theory (QFT), which is an essential prerequisite for studying quantum gravity. Weinberg's books are widely regarded as authoritative references on QFT, and studying them would give you a thorough understanding of the subject.
However, it's important to note that quantum gravity is a highly specialized and advanced area of theoretical physics. While mastering QFT is a crucial step, it is not the only requirement for studying quantum gravity. Quantum gravity involves the attempt to reconcile general relativity, which describes the gravitational force on a macroscopic scale, with quantum mechanics, which governs the behavior of particles on a microscopic scale.
To delve into quantum gravity, you would need to explore additional topics beyond QFT, such as general relativity, classical and quantum gravity theories, and mathematical frameworks like string theory, loop quantum gravity, or other approaches to quantum gravity. These topics are typically covered in more advanced textbooks and research papers.
Gaining expertise in quantum gravity is a long and challenging journey, requiring a strong background in theoretical physics, advanced mathematical skills, and an ability to grapple with complex and abstract concepts. It often involves active research and collaboration with experts in the field.