I built *BookTranslator.app* (https://www.booktranslator.app/) initially to help myself read English books in my native language. Later on as I shared on twitter, more and more people were finding it useful. So I thought it might also be helpful to share it here.

You can drag-and-drop an *EPUB or PDF (≤ 50 MB)*, pick one of *76 target languages*, and ~60 seconds later you get a layout-preserving translation plus a side-by-side bilingual reader.

The whole pipeline runs on the gpt-4o API with a bit of prompt-engineering to keep chapter structure, images and footnotes intact.

### Why I think it’s worth showing

* Most “AI translators” still force you to split books into chapters or plain text; I wanted true *one-click, whole-file* handling. * Speed: 100k words finishes in about a minute because translation requests are parallelised at the section level. * The bilingual view has proven handy for language learners and volunteer proof-readers.

### Tech stack

* *Frontend*: Next.js + Tailwind. * *Backend*: Node.js with GPT-4o calls

### Try it (no signup) There’s a *guest tier* without needing for signup and a *free tier)) providing 1,000 free credits so you can upload a small chapter or novella. Full pricing starts at a \$10/mo Pro plan.

### Looking for feedback 1. Accuracy vs. speed trade-offs – would you prefer a slower “highest-quality” model option? 2. Does the side-by-side reader help, or would you rather download just the translated EPUB/PDF? 3. Any edge cases (RTL languages, math formulas, EPUB3 media overlays) I should prioritise?

### Caveats & next steps * Still ironing out rare formatting glitches (tables, SVG images).

Thanks for reading—happy to answer anything!