I think Star Trek: Phase II - The Lost Series is also a decent book for reference.
Edward Gross' Trek: the Lost Years
is less professional looking (with no pictures either), but I recall it has a few things not in the authorized book.
The Gross book is missing a key part of the p2 puzzle that the authorized book does have (that folks at the top already knew the series wasn't going ahead, even while the sets were getting rushed and the scripts getting written), but other than that the Gross is LOADED with great info. The stuff from Joe Jennings is really great.