I spent 6 years studying math and physics in college. (I am not a PhD).<br>But, I have learned more about the "deep thinking" behind modern physics by studying the one book, then from all the other books combined. Penrose writes with that deep thinking in mind. While the book is 16 years old, it is still worth reading because it provides the historical, conceptual, and mathematical context behind existing "Unified Theory" efforts.