Thanks! Absolutely. You can invite users to your Storyteller server and give them whatever permissions are appropriate (e.g. you can choose whether they can only download books, or can also manage uploading and syncing books and/or managing users). It has SMTP support for emailing invites, or it can just generate invite links for you to share yourself.
More info here: https://smoores.gitlab.io/storyteller/docs/administering#inv...