Good introductory books for string theory?

[mathlete]

I'm not talking about Elegant Universe level, but something that would give a nice introduction into string theory and its theories (with math, of course) for beginners would be nice. Any ideas?

 

[josh1]

https://www.amazon.com/gp/product/0521831431/?tag=pfamazon01-20

 

[Kalimaa23]

Well, Zwiebach is very basic, but you'll still need some background in physics and mathematics. What is your current level of understanding mathlete?