Mike Holts Exam Guide. I am buying the 2008 edition soon, along with the dvd's. It's content way exceeds Californias JW, or Contractors exam requirements, but the info is useful for working in the field, especially when the responsibility is on you to install the work correctly. I had a copy of his 1997 edition, and even my father who was a vocational instructor said that it was a very good book. Good luck.