Don't worry! You get to control who can see your content!
Along with customizing shelf descriptions and appearances, you can share your shelf with other users. To do so, tap to open the shelf you want to share. Then tap the gear in the top right. Then tap the "Members" section.
Here, you can see the list of users who currently have access to that shelf. You can tap user names to view and manage their permissions.
By tapping the plus icon, you can add users by their email address. Tap "invite" to then determine their shelf permissions. Then tap the "save" icon in the top right.