Notebooks for iPhone Answers

Whenever you back up your iPhone/iPad through iTunes, all books and notes of Notebooks are backed up, too. A restore should usually bring them back. -- This is a process that is controlled by iTunes and cannot be influenced by Notebooks.

In some cases (after installing a new OS, for example) the first restore might just reinstall Notebooks but not its contents. If you restore from the latest backup again, then the contents should be brought back into Notebooks, too.