"Save to disk" will create a hierarchical directory structure. Let's say you have a directory called books where you save the ebook files. If you use "save to disk," the files will be saved within author/title subdirectories. For instance:
~/books/Ernest Hemingway/The Sun Also Rises/The Sun Also Rises.epub
If you use "save to disk in a single directory," the files will be dumped into the books directory with no subdirectories:
~/books/The Sun Also Rises.epub
|