Can I save the changes I've made to the Travel Book so I can continue editing later?

Si, yes, oui, ja! You can start editing your Travel Book and finish it at any other time. Just hit the "Save & Generate" red button to save your edits. The changes you make to the Travel Book will be saved for your next visit.
To continue editing after a big cup of coffee for example, or a night's sleep, just hit the create Travel Book button to generate the last edited version of your book.