
Barton Zwiebach
A first course in string theory
For the students wishing to work their way through the book, be warned  it's not the sort of work where you can skip some of the maths and still get an idea of what's going on (as you can with say Penrose's The Road to Reality). Rather it's necessary to work through the mathematics and complete each chapter before going on to the next (at least in the first part of the book). But it does start from a level which an undergraduate physicist should find understandable  the lagrangian of a piece of string  rather than jumping straight in with Quantum Field Theory. Relativity and quantum theory are then introduced when needed. Students who do work through this book will not just learn about a single candidate for a 'Theory of Everything', they will also get an understanding of much of the mathematics needed for the rest of modern physics