Toastaspiring/reader-x ? reverse-engineered prompt

Build me a clean offline book reader called ReaderX that works in the browser and can also be packaged as an Android app.

It should let me import EPUB and PDF files into one library, show covers and basic details like title and author, and let me search and sort my books. When I open a book, I want two reading modes, page turning and continuous scroll, with easy touch gestures, keyboard shortcuts on desktop, and a simple toolbar that can show the table of contents, change text size or zoom, and switch between light, sepia, and dark themes.

Please make it remember where I left off, keep everything stored on the device only, and work fully offline. EPUBs should render properly with images, styles, and embedded fonts, and PDFs should load smoothly too. I’d like it to feel mobile friendly, with a modern full screen layout. If you need current docs for the EPUB or PDF libraries, look them up online.