In terms of creating Screenbooks, the two programs are the same except that the free version puts a "www.screenbooks.net" label on all low resolution images. In the Pro version you can remove this label or make your own.

Screenbook Maker Pro also has additional image options, such as adding JPG images in addition to screenshots, and additional screenshot options, like area capture. Screenbook Maker Pro can also convert Screenbooks and bookshelves to PDF files. See the library page for some examples.