I use FBReader on a couple of Android 8" tablets and my phone, it'll connect to a calibre library and stores/syncs progress on Gdrive or Dropbox (wish that was more open). But its a great reader app.

I docker calibre/calibre-web/openbooks as follows and pull my books from usenet where someone has more than likely broken the DRM. I'm just going to say, I own every book I read on paper or Kindle, I just can't stand paper books and there's no way to convince these publishing co's to send me the ebook for the physical book.

When you use this, go into the Calibre app and set up the auto-import to the Data volume that is shared by the containers. Then when you download a book, you can just press cancel to save, as the book will be autoimpored from the temp folder in Openbooks by Calibre and deleted from the Data volume.

version: "2.1"
services:
  calibre:
    image: lscr.io/linuxserver/calibre:latest
    container_name: calibre
    environment:
      - PUID=0
      - PGID=0
      - TZ=America/Denver
    security_opt:
      - seccomp=unconfined
    volumes:
      - ./data:/config
    ports:
      - 7080:8080
      - 7081:8081
    restart: unless-stopped
    labels:
      - com.centurylinklabs.watchtower.enable=true

  calibre-web:
    image: lscr.io/linuxserver/calibre-web:latest
    container_name: calibre-web
    environment:
      - PUID=0
      - PGID=0
      - TZ=America/Denver
      - DOCKER_MODS=linuxserver/mods:universal-calibre #optional
    volumes:
      - ./data/web-config:/config
      - ./data/:/books
#      - ./data/Calibre\ Library:/books
    ports:
      - 7083:8083
    restart: unless-stopped
    labels:
      - com.centurylinklabs.watchtower.enable=true

  openbooks:
    ports:
      - 7082:80
    volumes:
      - './data/:/books'
    restart: unless-stopped
    container_name: OpenBooks
#    command: --persist
    command: --name "InsertSomeAliasHere" --persist
    environment:
      - BASE_PATH=/
    image: evanbuss/openbooks:latest
    labels:
      - com.centurylinklabs.watchtower.enable=true