$scope.nextStory = function () {
    var storyID = Number($routeParams.storyID);
    var path = 'stories/' + (storyID + 1 );
    $location.path(path);
};
$scope.previousStory = function () {
    var storyID = Number($routeParams.storyID);
    var path = 'stories/' + (storyID - 1 );
    $location.path(path);
};

http://website.co.uk/index.html#/stories/13