I read every single day. At home it's on my Kobo running KOReader (yes, I'm that open-source guy), and I love it. The problem: I don't always have the e-reader on me. On the train, at work, waiting somewhere — I just have my phone.
I tried Kobo's own Android app to bridge the gap and... I really didn't like it. Promos everywhere, adding your own books is a pain, the reader itself feels clunky, and the Wi-Fi handling is annoying.
So I built my own thing: Varbook, a small self-hosted EPUB library.
You drop EPUBs into it in one click. From there:
- They're readable on your phone through a simple but well-made PWA. Books are cached locally, so you can read offline; when you're back online your reading position syncs to the server.
- The server exposes everything over OPDS, so any compatible app works (KOReader, Moon+ Reader, etc.).
- I also wrote a KOReader plugin that pushes/pulls your reading position to the server in a single gesture.
My actual daily workflow:
- Evening, at home: I wake up my Kobo in KOReader, tap the top-right corner → Wi-Fi turns on, my current book jumps to the right position, Wi-Fi turns back off to save battery.
- I read.
- Done reading: tap the top-right corner again → Wi-Fi on, my reading time + position sync to the server.
- Next day, at work: I open the PWA on my phone. It drops me exactly where I left off, and syncs my position on every page turn.
- Evening: back to the Kobo, which picks up my position from the phone.
All of this with fully open-source software, no commercial service in the loop, my books staying on my own server.
The trickiest part was cross-device position sync — every reader engine (epub.js in the browser, KOReader's CREngine, Moon+) tracks position differently. Varbook uses a "pivot" format based on EPUB spine items (chapter index + percentage) so your position survives the jump from one device to another without throwing you 30 pages off.
It's open source (MIT), built with Laravel + React, and ships as a single Docker container (SQLite by default, no external DB needed). The entire UI is translated in English, French, and Spanish.
Honest disclaimer: a good chunk of this is vibe-coded. That said, I've been a developer for 20 years, so it's opinionated vibe-coding — I know what I'm looking at. It's been used daily and intensively by about 5 people for the last 3 months, and I keep improving it regularly. It's not bug-free, but I'd call it reasonably stable. I'm being upfront so you know what you're getting into.
There's a free public instance if you just want to try it without installing anything: https://varbook.hophop.be/
- Full write-up on my blog: https://trucs.hophop.be/en/blog/varbook-bibliotheque-epub-self-hosted
- Code: https://github.com/ndieschburg/varbook
- KOReader plugin: https://github.com/ndieschburg/varbook.koplugin
Happy to answer questions or hear what's missing — it scratches my own itch, but I'd love to know if it's useful to anyone else.
Don't let the anti-AI bullshit get you down. You built something that worked for you, it isn't the basis of national security for everyone and you wanted to share it. And you opensourced it so if I want to bolt on an IRC downloader or something, it's easy.
I appreciates you.
Debatable