malawi_glenn said:
I've hear many bad things about it, some consider Green & Witten's book "superstring theory" THE introductory textbook. But maybe the best is to start with Polchisnki's book after Zchwiebach due to its modernity?
Polchinski certainly has its flaws, but for a lot of people it is still the way to go. The problem with the book is mostly that it's vague and technical at some points - the book is definitely not suitable of the less-technical reader. I don't have much experience with GSW but yea, it is also considered a classic.
Zwiebach is a nice book, but aimed at undergraduates. It hardly treats topics like conformal field theory and a lot (and I do mean a LOT) is left out. This book doesn't (or hardly) requires experience in QFT and GR and it introduces some of this material.
Becker, Becker and Schwarz is also a good choice, but a little less deep than Polchinski. The biggest difference between this book and Polchinski (or Green, Schwarz and Witten) is that it's also a modern book and treats some of the more advanced topics (M-theory, gauge/gravity duality) which do not appear in the older books. This is nice, because it gives you an idea of where modern-day research (i.e. the problems) stands.
If you've had classes in GR and QFT you should skip Zwiebach altogether and start with Becker, Becker, Schwarz if you want to have a first, decent treatment on String Theory. If you really mean business skip to the more advanced texts such as Polchinski or Green, Schwarz, Witten. The latter books have a fairly steep learning curve though and you'll miss out on the modern day topics. But if you're really serious about learning string theory you eventually end up with these books anyway.
You can also follow the online class on this website (follows Polchinski Vol 1.):
http://www.pirsa.org/C09001
Edit: do note that GSW doesn't have any exercises.
