You can't rename a recipe book on a phone

Renaming only worked from the desktop sidebar's right-click menu, and not for the book you have open. Fixed for the next release: Rename is in Manage books (the pencil beside a book's name), in the phone's recipe book switcher, and in the right-click menu of the book you have open. Anyone in a book can rename it, since the name is your own label for it. Reported by a beta tester.