What is a privacy-specific reading management app?

I am looking for an app that can record the books I read. It is an application like Libib. https://www.libib.com/ I want an app that is more specialized in privacy and security. The necessary points are as follows.
Both Android and iPhone.
Is open source
Data to be saved is encrypted properly.
If there is a better point. (It is good even without)
It can be shared in the cloud.
When storing in the cloud, there is a function that can save the server on your own server or NextCloud or Google Cloud.