Calibre is a comprehensive e-book management application that functions as a library manager, format converter, metadata editor, device synchronization tool, and content server. The codebase is a large monolith written primarily in Python with C/C++ extensions for performance-critical operations (PDF rendering, character encoding detection, compression). It provides a full desktop GUI built on PyQt6, a CLI for headless operations (calibredb, ebook-convert), and an embedded HTTP/OPDS server for remote library access. The architecture follows a plugin pattern: format conversion (input/output plugins), device drivers (USBMS, MTP, dedicated reader drivers), store search plugins, metadata source plugins, and AI provider plugins (OpenAI, Anthropic, Ollama). The core database is SQLite with full-text search (FTS5). Extensively cross-platform (Windows, macOS, Linux) with platform-specific launcher code in C. While the codebase shows high craftsmanship in many areas (e.g., SQLite extensions, font parsing, AI abstraction), it also carries legacy components such as an old RTF parser, vendored libraries (tinycss, frozen), and some device drivers for obsolete readers. Overall, it is actively maintained with regular commits and responsive issue triage.
KOReader is a document viewer application primarily designed for e-ink readers, supporting a wide range of formats including PDF, EPUB, DjVu, CBZ, and more. It provides a full-featured reading experience with file management, annotation, dictionary lookup, OPDS catalog browsing, Calibre integration, cloud storage, and extensive customization through a plugin system. The architecture is a monolithic Lua application built on a custom widget toolkit with an event-driven UI manager, platform-specific device abstraction layers (Kindle, Kobo, PocketBook, reMarkable, Android, SDL), and a robust caching and rendering pipeline. Key entry points are `reader.lua` for the main application and `kodev` for development/testing. The codebase is large and mature, with a strong emphasis on performance and e-ink optimization, but shows some technical drift in the form of deprecated code paths, platform-specific hacks, and a fragmented keyboard layout system.
SimpleUI is a KOReader plugin that provides a highly customizable, distraction-free user interface overlay for the KOReader e-book reader application. It replaces the default homescreen with a modular widget system (clock, currently reading, recent books, reading stats, cover deck, etc.), adds configurable top/bottom bars, quick settings bar, library enhancements (virtual browsing, cover overrides), reading statistics and streaks with heatmaps, backup/restore, and over-the-air updates. The plugin is implemented in Lua and deeply integrates with KOReader's widget framework, extensively monkey-patching core classes like FileChooser, TouchMenu, and TitleBar. Despite heavy coupling to KOReader internals, the codebase exhibits strong engineering practices: lazy loading, parameterized module factories (e.g., GridRenderer), custom caching layers (cover cache, stats cache), a reusable anti-aliased drawing library, and a self-contained i18n system with PO file parsing. The repository is actively maintained with a well-documented public API for external plugins to register quick actions. It is not a standalone application but a plugin that must be installed within KOReader. The primary risk is reliance on KOReader's internal APIs, which may break with upstream changes.
Episteme is a modern, cross-platform e-book and document reader built with Kotlin Multiplatform and Compose Multiplatform. It supports a wide array of formats including EPUB, PDF, MOBI, audiobooks (M4B), FB2, DOCX, ODT, PPTX, and comic archives (CBZ/CBR). The app offers a rich reading experience with paginated and vertical scroll modes, text-to-speech, ink and text annotations, OPDS catalog browsing, cloud sync via Google Drive and Firestore, AI-powered summarization, and extensive customization (themes, fonts, brightness). The codebase is organized into a shared module containing core business logic, models, and policies, with platform-specific implementations for Android (native Compose, Room, WorkManager), iOS (Swift), and Desktop (Compose Desktop, Swing interop). The architecture follows a clean separation of concerns with expect/actual abstractions for platform services, making it a strong example of production-ready KMP application design.
This repository provides a Python CLI tool and Makefile pipeline to scrape all essays from Paul Graham's website (paulgraham.com), convert them to Markdown, and produce an EPUB ebook. The core logic resides in a single script (`graham.py`) that uses `requests`, `BeautifulSoup`, `html2text`, and `htmldate` to download, parse, and date-stamp each essay. A `Makefile` orchestrates the full build: creating a virtual environment, fetching essays, merging them with `pandoc`, and generating the final EPUB with a custom CSS and an iBooks dark-mode patch. The CI workflow (GitHub Actions) runs daily, detects new essays by comparing article counts, and automatically creates a release with the updated EPUB and metadata CSV. The architecture is straightforward—no web server, database, or tests—but the pipeline is robust and well-documented for its single purpose. While the scraper is tightly coupled to Paul Graham's site structure, several components (the iBooks patcher, the footnote conversion function, and the EPUB stylesheet) are cleanly isolated and reusable in other EPUB generation projects.
Koodo Reader is a cross-platform ebook reader application supporting a wide range of formats (EPUB, PDF, MOBI, AZW3, TXT, FB2, CBR/CBZ, MD, DOCX, HTML, etc.). It is built as an Electron desktop app with a React/TypeScript frontend and a separate Go HTTP server for OPDS catalog serving and KOReader sync. The application provides a full-featured reading experience including bookmarks, notes, highlights, text-to-speech (with multiple voice engines), translation and dictionary lookup (via built-in and custom plugins), OCR for scanned PDFs, and cloud sync/backup across many providers (WebDAV, S3, OneDrive, Google Drive, Dropbox, etc.). It also includes a library management system with shelves, tags, search, and import from local files, folders, URLs, and OPDS catalogs. The architecture is a monolith with a clear separation between the Electron main process (Node.js) and the renderer (React), plus an optional Go server for network-facing features. The codebase is large and feature-rich but shows signs of technical debt: widespread use of deprecated React lifecycle methods, heavy reliance on opaque minified libraries (kookit-extra), frequent `as any` type casts, and mixed Chinese/English comments. Despite these issues, the application is actively maintained and offers a robust set of features for ebook enthusiasts.
Elib2Ebook is a .NET 10 application that downloads books from 60+ online libraries (Litres, MyBook, BookRiver, etc.) and converts them into standard ebook formats (EPUB, FB2, CBZ, JSON, TXT). It is a dual-deployment solution: a CLI tool and a Blazor web UI, both sharing a core domain and service layer. The architecture is a layered .NET solution with Domain, DomainServices, and per-site ExternalServices projects, using a reflection-based GetterFactory to auto-discover site adapters. The system handles site-specific anti-bot measures, authentication, and pagination, then normalizes content into a common domain model before passing it to format-specific builders.
This repository implements a desktop application for batch processing EPUB ebooks, including reformatting, encryption/decryption (filename obfuscation), font encryption/decryption with OCR-based recognition, image compression and conversion, cover replacement, and Chinese text conversion. The application is built with Tauri 2 (Rust) as the desktop shell, Vue 3 with TypeScript for the frontend, and a Python sidecar for the heavy processing tasks. Communication between the frontend and Python backend uses a JSON Lines protocol over stdin/stdout, with protobuf schemas defining the message envelopes. The architecture follows a clear separation of concerns: the Rust layer manages the application lifecycle, window effects, and sidecar process; the Vue frontend provides a drag-and-drop interface with task panels, persistent state management, and custom UI components; the Python backend implements a task runner that dispatches work to specialized service modules for EPUB structure manipulation, font obfuscation with ONNX OCR inference, image processing, and text conversion. The system includes a comprehensive test suite covering unit tests, integration tests, and protocol contract tests. Notable design patterns include a reusable EPUB workspace abstraction with security validation, a protocol layer with dataclass-based request/response models, safe JSON serialization handling edge cases like lone surrogates, and Vue composables for persistent state and Tauri IPC bridging. The font encryption/decryption services demonstrate advanced CSS cascade emulation and glyph rendering with OCR, though they contain significant code duplication. The README explicitly states that this repository is historical and that EPUB capabilities have been migrated to a Rust implementation (epub_tool_rust). As such, the project is deprecated and no longer actively developed, but the codebase remains a well-structured example of a cross-platform desktop application with a Python sidecar.