Yes, otherwise it won't work since your device sees these two apps as the same one. If you're having trouble uninstalling it, just follow these steps:
1) Go to your device's Settings app > Apps > StoryScape > Clear Data.
2) Uninstall the official version of StoryScape from Google Play Store.
3) Run "Force Close" on both StoryScape and Storyscape Mod apps.
4) Reboot your device (it's pretty necessary).
5) Install StoryScape again from Google Play Store, then install this Mod in the same time by tapping on "[Update]" button.