How we tackled EPUB parsing and rebuilding for AI book translation, with code examples and hard-won lessons.
At LectuLibre (https://lectulibre.com), we translate books using AI. Users upload EPUB or PDF files, and our system translates the text inside while preserving the original formatting. Sounds straightforward, right? Well, we quickly learned that handling EPUB files in production is anything but trivial. In this article, I'll share the real-world challenges we faced parsing and rebuilding EPUBs with Python, the libraries we chose, the code we wrote, and the lessons we learned along the way.
The Problem: Translate Books, Not Just Text
An EPUB is essentially a ZIP archive containing HTML, CSS, images, and a manifest file (content.opf). To translate a book, we needed to:
Parse the EPUB's structure and extract translatable content.
