I think the use case is sustainable, it will compare with Steem but with a shop where one can buy/sell books. Let's see how the dev team responds and the community operate on this project.
There is always room for similar projects in the world, just as long as the team can deliver on what they have planned. I really believe in this team which is why I support them 100% and will continue to support the team as Glacier is a long term project. I think we all will get a good idea on how well the project will do once the blogging platform is launched.