Install epubcheck by entering the following commands in the terminal:
sudo apt update sudo apt install epubcheck
Description:
Validation Tool for EPUB
EpubCheck is a tool to validate IDPF EPUB files. It can detect many types of errors in EPUB. OCF container structure, OPF and OPS mark-up, and internal reference consistency are checked. EpubCheck can be run as a standalone command-line tool, installed as a Java server-side web application or used as a Java library.
Homepage: https://github.com/IDPF/epubcheck
Version: 4.0.2-2
Section: universe/text