I know the concept behind String Theory. But I was wondering if anyone knows of a good place to start learning more about the theoretical physics behind it? Maybe a book someone can recommend to me! I have a strong mathematical background, so something abstract is fine for me. I also know quite a bit about physics.
If you want an overview over string theory without any! mathematical background, I can still recommend Brain Greens "the elegant universe".
A real book on String theory is "Barton Zwiebach- A first course in string theory" It starts very slow and develops the math behind the theory from the very beginning. Even if you have a strong mathematical background, I think it's worth to read it, because it is completly adapted to what you need in string theory. I didn't finish it but I liked it.