A First Course in String Theory

Steven Gubser Yes. This is a book by my MIT colleague Barton Zwiebach, and it grew out of a year-long course that he taught at MIT for undergraduates who wanted to learn string theory. So he goes through a lot of the material that the Green, Schwarz, Witten and Polchinski books cover at a more detailed level. He does it without any claims of completeness, but you really do get the idea. I remember when I learned string theory myself, the thing that was hard was that you seemed to have to learn every idea three or four times over, because everything had been thrashed out with different methods, by different... (Source)