I have read "Theory of Everything" and understood  the technical elements of physics by Brian Greene.  Becker2,Schwarz are math professors first.  Reader beware.  You must have a desire for string knowledge or math interests.  Yes the book is great.  Beware amatures. I have also resad "String Theory" by Joseph Polchinski.  I understood more material but it is almost 10 years old.  Big difference. I recommend reading such a up-dateded version of brane data. So much more too.