         delete @_savingTimeout
       ), SAVE_DELAY
 
-
+    # A book is not loaded until the navModel is loaded.
+    # Once the navModel is loaded, "autosave" whenever it changes.
     _loadComplex: (fetchPromise) ->
       fetchPromise
       .then () =>

    branch: true # This element will show up in the sidebar listing

    initialize: () ->
      super {root:@}

      # Contains all entries in the OPF file (including images)

      # This is useful when the OPF file was remotely updated
      @_localAddedItems[model.id] = model

    # Called on "autosave".
    # Only save the navModel and new files (and all the OPF files).
    # Delay the save and if more than one thing changed during SAVE_DELAY
    # only save once.
    #
    # Reason for SAVE_DELAY: a "move" is 2 operations, `remove` followed by `add`
    _save: ->
      clearTimeout(@_savingTimeout)
      @_savingTimeout = setTimeout (() =>
