|
An intelligent EPUB reading companion that doesn't just hold your books, it understands them. |
- Overview
- What's New in 4.0
- Key Features
- Screenshots
- How Aira Works
- Technical Architecture
- Setup & Installation
- Contributing
- License
- Contact & Support
Quill reimagines what a reading app can be. It pairs a carefully crafted EPUB reader with Aira, an AI reading companion that reads along with you. Aira answers questions about your book straight from its pages, explains difficult passages, helps you keep track of characters, and can even paint a scene you're reading, all without ever spoiling what comes next.
Bring your own EPUBs or pick from thousands of free classics on Project Gutenberg and Standard Ebooks, set the mood with ambient soundscapes, and build a steady reading habit with reminders and insights.
- Meet the New Aira: rebuilt from the ground up. Aira knows whether you're asking about your book or anything else, answers straight from the pages you've read, never spoils what's ahead, and can read her answers aloud.
- Ask Aira From the Page: select any word or passage while reading to define words, explain tricky lines, or find out why a moment matters, without leaving the book.
- Character Companion: select a character's name to recall who they are, see what they're up to lately, or trace their whole journey so far. Always spoiler-free.
- Visualize Scenes: turn any passage into a painted illustration, kept in a Visuals gallery that takes you right back to the passage it came from.
- Highlights: a smoother way to select text, plus highlights you can revisit from one place and jump straight back to.
- A Reimagined Reader: new reading settings, a cleaner table of contents, a warm night light, and page turning with your volume keys.
- Ambient Sounds: six soundscapes, from gentle rain to a crackling fireplace. Preview them before you play, or have them start automatically when you open a book.
- Reading Reminders: a daily reminder at the time you pick, or playful nudges to keep your streak going.
- Discover & Organize: a redesigned Discover tab, better Project Gutenberg and Standard Ebooks browsing, a quick way to add your own books, and categories you can reorder by dragging.
- Reading Insights: reading time, streak, peak reading hours, favorite authors, and how you read with Aira, all on a refreshed Insights screen.
- A Fresh Look: a brand new app icon and splash screen, the new Harbor color theme, and a polished feel across the whole app.
- Grounded in the text: Aira answers from the actual passages of your book, retrieved on-device, not from guesswork.
- Spoiler lock: her knowledge is locked to your reading progress. She never reveals events from chapters you haven't reached.
- Smart routing: Aira works out whether you're asking about your book or about something general, and answers each the right way.
- Full conversations: chat naturally about the plot, characters, themes, or world-building. History is kept per book, with a clear current-chapter header.
- Read aloud: listen to any of Aira's answers, spoken with natural-sounding text-to-speech.
Select text while reading and the Aira peek bar offers quick actions based on what you picked:
| You select | Quick actions |
|---|---|
| Nothing | Summarize chapter · Who are the characters? · What are the themes? |
| A word | Define · What is this? |
| A name | Who is this? · Recent Role · Journey So Far |
| A short phrase | Explain this |
| A passage | Explain this · What's the significance? · Visualize this |
- Character companion: recall who a character is, see what they're up to lately, or trace their whole journey through the story so far.
- Chapter summaries are built from the full chapter text, and theme questions consider the current chapter alongside the rest of what you've read.
- Answers type out smoothly, and if you select something that isn't a character's name, Aira kindly tells you so.
- Turn any descriptive passage into a painted, oil-style illustration.
- Every image is saved to a per-book Visuals gallery.
- Go to Passage jumps straight back to the exact spot in the book the image came from.
- Readium-powered EPUB engine with smooth chapter navigation and accurate progress tracking.
- Reading settings: fonts, text size, spacing, page themes, and paged or scrolling layout.
- Custom text selection and highlights, with a Highlights screen to revisit every highlight and jump back to it.
- Table of contents sheet, progress slider, and resume-where-you-left-off.
- Night light: a warm amber tint for comfortable late-night reading.
- Volume-key page turning.
- Six soundscapes: Forest, Rain, Brown Noise, Fireplace, Library, Riverside.
- Preview sounds before playing, start and stop from the reader overlay, and optionally auto-play on open. Volume follows your device's own volume controls.
- Seamless looping with crossfades.
- Import your own EPUBs from anywhere on your device.
- Project Gutenberg: browse, search, and download 60,000+ free books.
- Standard Ebooks: carefully formatted, high-quality public domain editions.
- Discover tab with a hero carousel and curated shelves.
- Categories: organize books your way, with drag-and-drop reordering.
- Storage management: see how much space each book uses and clean up.
- Reading insights: time read, day streak, books finished, a reading heatmap, peak reading hours, favorite authors, library progress, and your Aira activity.
- Daily reading reminder at a time you choose, plus optional playful reminders to keep your streak alive.
- Multiple color themes (including Harbor), light and dark modes, AMOLED black, and dynamic color.
- Cloud sync of your library and categories across devices via Firebase.
- Profile with display name and avatar.
| Basic Reader | Quill Pro | |
|---|---|---|
| Full reader, sources, sounds, highlights, insights | ✅ | ✅ |
| Daily Aira queries | 5 | 50 |
| Visualize (3 queries per image) | ✅ | ✅ |
Quotas reset daily. Subscriptions are handled through Google Play Billing.
Library |
Discover |
Book Details |
Reader |
Ask Aira From the Page |
Aira Chat |
Reading Settings |
Insights |
Aira combines on-device retrieval with server-side generation. Your book is indexed on the phone; only the handful of relevant passages for a given question are sent to the model.
When a book is added, a background worker (WorkManager) processes it:
- The EPUB is split into chunks of about 1,500 characters with a 250-character overlap.
- Each chunk is embedded with BAAI/bge-small-en-v1.5, running locally through ONNX Runtime.
- Chunks and their embeddings are stored in Room, with an FTS4 full-text index alongside.
- Hybrid search: semantic vector similarity and FTS4 keyword matching, merged with Reciprocal Rank Fusion.
- Spoiler lock: retrieval is capped at the reader's current chapter, so passages from unread chapters are never sent.
- Action-specific strategies for the character tools:
- Who is this? takes the character's first mentions verbatim, then spreads picks evenly across your reading progress in zones, ranked by how much each passage actually describes them (personality, role, relationships, appearance).
- Recent Role uses their latest appearances.
- Journey So Far splits their arc 20/60/20: their introduction, a scattered and semantically ranked middle, and their most recent scenes.
- Overlapping duplicate chunks are removed, and a per-chapter cap stops any single chapter from dominating.
- Chapter summaries read the chapter straight from the EPUB rather than stitching overlapping chunks back together.
Retrieved passages and a task-specific prompt go to Firebase Cloud Functions, which call Google's models:
| Task | Model / Service |
|---|---|
| Chat, quick actions, intent routing | Gemini 2.5 Flash-Lite |
| Visualize (illustrations) | Gemini 2.5 Flash Image |
| Read aloud | Google Cloud Text-to-Speech |
Prompts enforce strict grounding and attribution: Aira states only what the passages show, never borrows a detail from a different character, and stays spoiler-free.
Quill uses a multi-module MVVM + Clean Architecture setup.
Quill/
├── app/ Main app: navigation, library, sources, Aira chat, insights, settings,
│ notifications, billing & quota, cloud sync, onboarding
├── reader/ Readium-based EPUB reader: engine, overlay, settings, highlights,
│ ambient sounds, Aira peek bar
├── aira/ AI layer: RAG retriever, ONNX embeddings, chunking, intent detection,
│ book / general / quick chat services, voice output
├── database/ Room database, DAOs, entities, FTS4 index, migrations
├── domain/ Shared models and repository interfaces
├── theme/ Design system: color schemes, typography, design tokens, haptics
└── functions/ Firebase Cloud Functions (TypeScript): bookChat, generalChat, quickChat,
detectIntent, visualizeScene, speakText
Language: Kotlin 2.3
UI: Jetpack Compose, Material 3 Expressive, Haze (blur), Coil
Architecture: MVVM + Clean Architecture (multi-module)
Dependency Injection: Koin
EPUB Engine: Readium Kotlin Toolkit
Local Storage: Room (+ FTS4), DataStore
Background Work: WorkManager, AlarmManager
Audio: Media3 ExoPlayer
Embeddings: BAAI/bge-small-en-v1.5 via ONNX Runtime (on-device)
AI Models: Gemini 2.5 Flash-Lite, Gemini 2.5 Flash Image
Speech: Google Cloud Text-to-Speech
Networking: Ktor (Gutendex API, Standard Ebooks OPDS)
Backend: Firebase Auth, Firestore, Cloud Functions, Crashlytics, Analytics
Payments: Google Play Billing
Concurrency: Kotlin Coroutines & Flow
Min / Target SDK: 26 / 37
- Android Studio (latest stable recommended)
- JDK 17 or higher
- Android SDK with API 37 installed (the app runs on API 26+)
- Node.js 24 and the Firebase CLI (for Cloud Functions)
- A Firebase project on the Blaze plan (required for Cloud Functions and outbound API calls)
git clone https://github.com/MohammadAliUstad/Quill.git
cd Quill- Create a project in the Firebase Console.
- Add an Android app with the package name
com.yugentech.quill. - Download
google-services.jsonand place it in theapp/directory. - Enable Authentication, Firestore, and Crashlytics.
cd functions
npm install
# Gemini API key used by the chat, intent, and Visualize functions
firebase functions:secrets:set GEMINI_API_KEY
firebase deploy --only functionsFor read aloud, enable the Cloud Text-to-Speech API in the Google Cloud project linked to Firebase.
Place the ONNX export of bge-small-en-v1.5 and its tokenizer in the aira module's assets:
aira/src/main/assets/model.onnx
aira/src/main/assets/tokenizer.json
- Open the project in Android Studio and sync Gradle.
- Select a device or emulator.
- Click Run
▶️ .
Quill Pro (optional): to test subscriptions, create a subscription with the product ID
quill_pro_monthlyin the Google Play Console.
Contributions are what make the open source community such an amazing place to learn, inspire, and create. Any contributions you make are greatly appreciated.
- Fork the project
- Create your feature branch (
git checkout -b feature/AmazingFeature) - Commit your changes (
git commit -m 'Add some AmazingFeature') - Push to the branch (
git push origin feature/AmazingFeature) - Open a pull request
Distributed under the Apache License 2.0. See the LICENSE file for details.
If you run into an issue or have an idea for a future update, please open an issue on GitHub or contact the developer directly.
Developer: Mohammad Ali Ustad
Email: Mohammadaliustad@gmail.com
Company: Yugen Tech
Built with ❤️ by Yugen Tech