There should be enough memory in the eDGe at the beginning without an additional memory card. Fresh out of the box the systems have a little over 2GB and a standard novel might be in the 500KB to 1MB range; thus allowing for several thousand eBook novels (or at least a few hundred big text books).
Have you tried retrieving a free eBook from a more generic resource like The Gutenberg Project?
http://www.gutenberg.org/wiki/Main_Page
This can be a relatively safe and inexpensive way to get used to downloading eBooks and using.