The Unofficial Guide to Walt Disney World 20xx (2013 right now) is the most informative book for planning. It will tell you (in its 800+ pages) almost everything you need to know and then some. It's the Disney Planning Bible, IMO. You can use it as a reference book and not slog through all of it...but it's well-written. I have read all of it and not been bored out of my skull. Seriously.
Birnbaum's Official Guide is Disney's book. It has very little planning advice and some of what it does have is just wrong. But it has very peppy descriptions of the rides and shows. It is brightly colored with loads of character clip art and nice pictures. The pages are smooth and shiny. It's the best "fun" book.
The Unofficial Guide people have a "color companion" that doesn't have all the info of the big book, but has a good amount of the best info, lots of color, shiny pages and nice pics. It's funny, too. If you don't want to buy the 800 pager AND the Birnbaum book, this is an excellent blend of the two and the one I'm now advising friends to get.
The Passporter lacks all the info of the Unofficial Guide and is not as fun and peppy as either of the color books. I don't think it's all that great.
The Complete Guide is more for Disney fans than Disney planners. I like the book, but I wouldn't buy it to help me plan a trip.