gistfile1.js

    ABS.Model.PassagePanel = Backbone.Model.extend({
        initialize: function () {
            this.updateBooks();
        },

        updateBooks: function () {
            var that = this,
                versions = new ABS.Collection.VersionList(ABS.bootstrap.versions),
                getBookOrd = function (book) { return book.get('ord'); };

            var version = versions.get(this.id);
            version.books.fetch({
                success: function (books) {
                    var attributes = {};
                
                    _.each(books.models, function (book) {
                        book.chapters.fetch();
                    });
                    
                    attributes.books = books.models;
                    that.set(attributes);
                }
            }); 
        }           
    });