hi triwy and welcome !
you might want to wait a little while before you buy a memory card ; many people find the internal memory is big enough to hold quite a lot of books, and the more books you have on your cybook the more difficult it becomes to navigate through the library. so you might decide you don't need one after all.
but if you do want one, try doing a search through the cybook forum to see what other people are using, or post your question in there ; i'm sure you'll get plenty of recommendations.
