I am in the last year of MSc. and would like to read string theory. I have the Zwiebach Book, but along with it what other advanced book can be followed, which can be a complimentary to Zwiebach. I would like a more mathematically rigorous book or lecture notes along with Zwiebach.
The canonical textbook is the two-volume set by Polchinski. David Tong has very nice notes up following this text.
You should be able to find various review articles on the arXiv as well, for instance:
Hope that helps...
Mathematical rigor is not the most important thing when first learning strings, there are many things that are not possible to formulate rigorously, because the best language for doing this isn't known. In addition to Polchinsky (which is excellent), I recommend reading Green Schwarz and Witten, and also the original papers, since these have points of view which are not found in later articles, but are profound and important.
These are found in two very good reprint volumes: "Dual Models", and "Superstrings" (although much of vol II is well covered in Green Schwarz and Witten and Polchinsky). These are essential for properly understanding the subject, even today. The issue is the Regge ideas and the S-matrix ideas which are glossed over in later treatments.