The ICC has provided free access to many of their codes. See below for details:
Steven Winkel & Francis D. K. Ching have written an illustrated interpretative guide to the International Building Code for each of past five editions (2015, 2012, 2009, 2006, 2000). These are extremely helpful at deciphering the technical and legal jargon contained in the actual International Building Codes. The edition for the 2012 Code is available as an ebook.
Journal databases are good resources of articles discussing changes to building codes.