Using the steps in this extension's documentation, you can prepare a beautiful and robust book from your genealogy data in a GEDitCOM II file. The book will be organized into chapters by generations, have a table of contents, an index, a bibliography of all cited sources, and include portraits of individuals. Click here to see a sample book created from the "Windsors" file included in the GEDitCOM II installation.
The typesetting of the final book is not built in to GEDitCOM II. Rather, all the hard work is done by the advanced typesetting system call LaTeX, which means to create books you have to install LaTeX on your Mac (it is free an easy to install). Once installed, you can then typeset books without knowing much about how LaTeX works. If you do know LaTeX, however, you can then take advantage of more advanced features and more easily handle any problems that arise in the typesetting process (i.e. you may need to learn something about LaTeX to handle all your book needs).