For general reference and all sorts of great info about the Revit API, I recommend:
- The Revit API Developer’s Guide Wiki at http://wikihelp.autodesk.com/index.php?title=Revit/enu/2013/Help/00006-API_Developer%27s_Guide.
- The RevitAPI.chm help file. This is part of the Revit SDK (Software Developers Kit) which is included in the Revit install in the ‘Install Tools and Utilities’ option on the install main page. Or you can download it at https://boostyourbim.wordpress.com/2013/02/16/download-links-for-the-revitapi-help-files/