I have not made the stacked books. I would assume that you do use cardboard inbetween and dowels for support. I do not think that the bottom is covered in fondant but am only guessing. I would guess that something like powdered sugar or buttercream is used between the top fondant and the cardboard to keep them from sticking together and ripping the fondant when the cakes are taken apart to serve. Again just a guess hopefully someone who has done this will respond. Good Luck!!
Hope this may help you?
http://thefrostedcakencookie.blogspot.com/search/label/how-to/
Edited to say that I would use a thin cake board under the book cake that goes on the top and some dowels on the bottom cake. 
Here is a link to all the book ideas you could want!
http://www.cakecentral.com/cak.....8199-.html
again I want to thank everyone who replied! I hope I dont screw this one up. I feel better knowing a bit more on how to do it.Ive only been making cakes for about 5 years, at 4 to 6 a year for family and friends. Ive had some come out great and some be a dissaster. I guess thats the way the cake crumbles.
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