The Calibre library server allows you to:

• Share your books with others.
• Easily transfer your books between devices and access them from anywhere.

Install the Calibre package. You might also want rsync to upload books.

apt install -y calibre rsync
mkdir /opt/calibre

Upload your local library (using rsync) to /opt/calibre/ and save the command somewhere.

rsync -avuP --delete-after ~/local_library/ root@example.org:/opt/calibre/server_library/

Then add a new user to protect your server:

calibre-server adduser name

Create a new file /etc/systemd/system/calibre-server.service and add the following:

[Unit]
Description=Calibre library server
After=network.target

[Service]
Type=simple
User=root
Group=root
ExecStart=/usr/bin/calibre-server --enable-auth --enable-local-write /opt/calibre/library --listen-on 127.0.0.1

[Install]
WantedBy=multi-user.target

to apply the change:

systemctl daemon-reload 

Enable and start the service.

systemctl enable calibre-server
systemctl start calibre-server

Create a new file /etc/nginx/sites-available/library and enter the following:

server {
    listen 80;
    client_max_body_size 64M; # to upload large books
    server_name library.example.org ;

    location / {
        proxy_pass http://127.0.0.1:8080;
    }
}

Then symlink to sites-enabled:

ln -s /etc/nginx/sites-available/library /etc/nginx/sites-enabled

Then issue a Let's Encrypt certificate.

certbot --nginx

Now add the DNS Records to point the calibre-sever to your name-server.

Now just go to library.example.org, the server will request the username and password you've set above.

ENJOY!