The simplest way to backup your data is with the built-in backup feature found under the Export option. Using that feature will automatically create a copy of your DVDpedia data folder, compress it into a .zip file and save it in the same location as your data folder. For added security, you can then move that .zip file to an external hard drive or burn it to a disc.
Or if you have a MobileMe account, you can automatically backup your Bookpedia data with Backup 3 using QuickPick. (http://bruji.com/articles/2008/02/21/did-you-know-quickpick/)