Readings from the 2011 NEC Codebook
Some people read poetry, but here is a reading that can really make a difference:
Readings from the 2008 NEC Handbook
NEC is the National Electric Code and is published by the National Fire Protection Association.
Article 690 is for Solar Photovoltaic Systems.
Readings from the NABCEP Study Guide for Photovoltaic System Installers Version 4.2-April 2009
These readings should be helpful when studying for the NABCEP PV Installers Exam or for other PV studies.