I just picked up a copy of the 2006 version of Birnbaum's Disneyland Resort: Expert Advice from the Inside Source, published by Disney Enterprises, Inc.
Let me quote from page 5, in the "A Word from the Editor" letter written by Jill Safro. Second Paragraph, second and third sentence.
While Disneyland Park is wonderfully familiar to us - practically a second home - Disney's California Adventure is a newer playing ground, and finding the best ways to take it in is an adventure in itself. (Even now, it remains a work in progress, with attractions such as the Twilight Zone Tower of Terror being added to further guest satification.)