The Best Sources
Becker, Becker, Schwarz, String Theory and M-theory has a wide scope (from classical bosonic strings to BFSS Matrix theory (and a bit of Matrix string theory), and a bit about F-theory) and discusses the topics very intuitively. I've not read GSW, but I've heard that BBS is a modification to that (old) book. Can be downloaded from http://www.gen.lib.rus.ec (not a pirate).
McMahon String Theory Demystified has a rather wide scope but relatively less depth. Could once be downloaded from a pirate site, which no longer exists.
Mohaupt Introduction to String Theory has a limited scope and depth, but covers the gravitational implications of string theory rather deeply. Can be downloaded here: http://arxiv.org/abs/hep-th/0207249v1.pdf
Kaku Strings, Conformal fields, and M-theory is an extremely rigorous, rather unintuitive, rather wide and deep, source for learning string theory.
Two More Sources
For String Field Theory
I am planning to read this lecture notes with a supposedly better (PDF only, no abstract page) version here.
Also, these lectures by Shiraz Minwala were suggested by Larry Harson in the comments.
This post imported from StackExchange Physics at 2014-03-07 16:40 (UCT), posted by SE-user Dimensio1n0