This book introduces the reader to the basic mathematical structures of theoretical physics: mainly Quantum Mechanics, Electromagnetic Theory, And Classical Mechanics. I used this at UC San Diego for a year long graduate course on Mathematical methods in physics and engineering. If one has the time, there is really a lot to be gained by carefully studying this book. A big part of the book is geared toward developing in detail the mathematics of the Quantum Theory. This is a good thing because in my experience most QM books are too eager to "get to the physics". It is true that you can get by with a superficial understanding of functional analysis and still do QM, but this book will give you an immensely deeper understanding of the underlying structure of the theory. In particular, the treatment of Green's functions and integral equations is good. There is chapter on Group Theory and it's uses in QM. Also is a chapter on Complex analysis, although it is a wise idea to read a book entirely devoted to this subject. Overall, I like this book very much.