A listing of the catalog fields as implemented by MAST,(which includes a few columns added by MAST staff), is available from the KIC field description page.
An ASCII version of the KIC can be downloaded via ftp or http at archive.stsci.edu/pub/kepler/catalogs
The published paper describing how the Kepler Input Catalog contents was determined: Kepler Input Catalog: Photometric Calibration and Stellar Classification Brown, T., et al, 2011.