Books

   

   
My favourite books to learn about String Theory
   

• Green-Schwarz-Witten
Superstring Theory
(vol. 1 and 2)
• Polchinski
String Theory
(vol. 1 and 2)

   

   
There is also a very recent book on CFT that looks worth having a look
   

• Blumenhagen-Plauschinn
Introduction to Conformal Field Theory - With Applications to String Theory (online Springer Link)