I posted a ? a few days ago inquiring how to make a book cake.
This: http://www.justbakedshop.com/blog/2010/03/09/adoption-day-cake/ is what my friend would like her cake to look like. She only needs it to serve about 15 people.

I'm trying to decide what pan size to use. Thinking of making one layer 9x13 for the entire book, torting it and filling it. My question reallly is whether its possible to do a filled book cake with just one layer (torted and filled) or if I need two cake layers for the right height.

I've never done any carved cakes before - hopefully this is an easy one to start with. I just am having trouble with pan size and layers...

That's the Wilton small book pan. You bake it in that shape. And it's the right size, 15-20 servings. Easy.

unfortunately, I don't have time to order the small book pan btwn now and when I need to make the cake. Could torting and filling one layer of a 9x13 achieve a similar (though smaller) effect? Or, do I need to really use two layers?

How tall is your 9X13? Personally, I would make 2 layers because you need the height to carve off enough to get the curve.