When I first decided to write a book on string theory, more than ten years ago, my memories of my student years were much more vivid than they are today. Still, I remember that one of the greatest pleasures was finding a text that made a difficult subject accessible, and I hoped to provide the same for string theory.
Thus, my first purpose was to give a coherent introduction to string theory, based on the Polyakov path integral and conformal field theory. No previous knowledge of string theory

Foreword
Preface
Notation
1 A first look at strings
1.1 Why strings?
1.2 Action principles
1.3 The open string spectrum
1.4 Closed and unoriented strings
Exercises
2 Conformal field theory
2.1 Massless scalars in two dimensions
2.2 The operator product expansion
2.3 Ward identities and Noether's theorem
2.4 Conformal invariance
2.5 Free CFTs
2.6 The Virasoro algebra
2.7 Mode expansions
2.8 Vertex operators
2.9 More on states and operators
Exercises
3 The polyakov path integral
3.1 Sums over world-sheets
3.2 The Polyakov path ingegral
3.3 Gauge fixing
3.4 The Weyl anomaly
3.5 Scattering amplitudes
3.6 Vertex operators
3.7 Strings in curved spacetime
Exercises
4 The string spectrum
4.1 Old covariant quantization
4.2 BRST quantization
4.3 BRST quantization of the string
4.4 The no-ghost theorem
Exercises
5 The string S-matrix
5.1 The circle and the torus
5.2 Moduli and Riemann surfaces
5.3 The measure for moduli
5.4 More about the measure
Exercises
6 Tree-level amplitudes
7 One-loop amplitudes
8 Toroidal compactification and T-duality
Appendx A: A short course on path integrals
References
Glossary
Index