# Smart Book — full documentation

> Smart Book is a bilingual ebook reader for language learners. It shows the original text and its translation side by side and lets you tap any word, sentence, paragraph or whole chapter for an instant, context-aware translation while reading. You can switch between many translation engines and AI models in one tap, save unknown words (with their context) to a personal dictionary for spaced-repetition review, listen to native-speaker and AI pronunciation, and read either a free library of bilingual stories or your own FB2 / EPUB / TXT files (and `.srt` subtitles imported as parallel text). Free, ~100 languages, available on iOS and Android. Developed by Stanislau Kurs (KursX); Android package `com.kursx.smartbook`, iOS App Store id `1278697399`.

This is the extended companion to [llms.txt](https://smart-book.net/llms.txt). It inlines the full feature set, the AI/translation stack, the app's backstory, platform notes, and the public how-to library.

## At a glance

- **What it is:** a bilingual / parallel-text ebook reader for language learners (Education category).
- **Developer:** Stanislau Kurs (KursX).
- **Content languages:** ~100 (for reading and translation).
- **Price:** free, with paid plans — PRO (one-time payment) and MAX (subscription).
- **Android** — store title "Bilingual Books: Parallel Read", package `com.kursx.smartbook`: 1M+ downloads, 4.7★ (~29.6K reviews), rated PEGI 3, contains ads and in-app purchases.
- **iOS / iPadOS / Mac** — App Store title "SmartBook: Dual Language Books" (id `1278697399`), by Stanislau Kurs: rated 4+, ~100 MB, requires iOS 16.4+, interface in English + 15 more languages.

(Store stats above are point-in-time snapshots from mid-2026 and will drift.)

## What Smart Book is

Smart Book turns reading foreign books into a language lesson. Instead of switching to a separate dictionary or translator app, you read in the app and translate in place: long-tap a word to see a translation that takes the surrounding sentence into account, select a phrase to translate it across several services at once, or auto-translate an entire chapter into parallel text. Original and translation sit side by side so reading stays natural while comprehension is always one tap away.

The core idea — and the reason the app was built — is **context-aware translation**. A plain dictionary returns a list of senses; Smart Book sends the whole sentence to an AI model so the translation fits the actual context, explains idioms, and clarifies meaning. The developer's original motivation (described on Habr) was comparing engine output: when a conventional engine like DeepL returns something unclear, you compare it against an AI translation to get the meaning that actually fits.

## Backstory

Smart Book began as an Android reader focused on parallel translation. Its defining moment was integrating the ChatGPT API to deliver context-aware, in-sentence translation rather than isolated dictionary definitions — letting readers understand idioms and ambiguous words in context. Since then it has grown into a multi-engine, multi-AI reader with a personal dictionary, audio, custom AI actions, and a cross-platform rewrite (Kotlin Multiplatform / KMP) bringing the iOS version up to parity with Android. The full story is told in the developer's Habr articles (linked below).

## Features in detail

### Reading
- **Parallel / bilingual reading** — original text and translation displayed together; read in two languages at once.
- **Your own books** — built-in reader for FB2, EPUB and TXT, including picture books.
- **Free book library** — a large, regularly expanded catalog of free titles (75,000+ public-domain books) plus bilingual stories and articles across many languages.
- **Library organization** — sort books into folders, rate books, and filter, sort and search the library.
- **Subtitles → books** — import `.srt` subtitles from any movie or video and read them as a bilingual book.
- **Share-to-translate** — translate text selected in other apps by sharing it into Smart Book.
- **Reading comfort** — Bionic Reading mode, custom fonts, savable custom themes, text formatting by width, in-book search, a word-occurrence counter (see every place a word appears and how many times), swipe-to-adjust brightness, and home-screen shortcuts to a current book.
- **Reading habit** — track consecutive reading days (reading streak).
- **E-reader friendly** — works on Android e-ink readers such as Onyx Boox.
- **Offline mode** — read, and translate selected text, with no internet connection.

### Translation
- **Tap to translate** — long-tap any word for an instant translation; select a sentence, paragraph, or highlighted span; or auto-translate a whole chapter.
- **Context-aware** — translations account for the sentence the word appears in, not just the word in isolation.
- **Compare engines** — view the same text translated by several services side by side and switch between them in one tap.
- **Multiple ways to reach the translator screen** — from various places in the app and the device.
- **Change translation language on the fly** while reading.

### Translation & AI engines
Built-in engines and models include:
- **AI models:** ChatGPT (OpenAI), Claude (Anthropic), Gemini (Google), DeepSeek, Perplexity.
- **Translation engines:** Google Translate, DeepL, Microsoft Translator, Yandex, Reverso Context, Lara, Papago, LingvaNex, NLP, Oxford (audio pronunciation / dictionary).
- **Bring your own:** connect any OpenAI-compatible AI service (any model that speaks the OpenAI chat protocol), or reach models via aggregators such as Hugging Face, OpenRouter, or Chutes, using your own API key.

### AI capabilities
- **Word & phrase insight** — definition, etymology, explanation, usage examples, and synonyms for any word.
- **Grammatical analysis** of any selected text.
- **Custom AI actions / prompts** — create any number of your own AI actions with your own prompts, and assign a different action to each trigger independently: word tap, paragraph button, text selection, and auto-translation. For example, show a definition on word tap, a translation on the paragraph button, an explanation on selected text, and a grammar breakdown on auto-translate — in any combination. System AI actions you don't use can be disabled.
- **Text simplification** — ask the AI to rewrite a passage at a target proficiency level (e.g. A1).
- **AI as a translator** — use any connected AI model for automatic translation.

### Dictionary & vocabulary
- **One-click save** — save any word to your dictionary with a single tap, together with the sentence it came from (context).
- **Learned words** — mark words as learned and highlight them in a different color; batch-mark every word in a chapter as learned in a few taps.
- **Export / import** — export selected words to a file; export to Anki or ReWord for spaced-repetition review; import learned words back.

### Pronunciation & audio
- **Native-speaker audio** — listen to the pronunciation of tapped words.
- **Text-to-speech** — paragraph-level TTS with customizable voices.
- **AI voice** — use AI-generated voices for pronunciation.
- **Custom pronunciation sequences** — set any number of source/translation pronunciations in any combination and order.
- **Chapter → audio** — convert a book chapter into an audio file.

## Supported languages

English, Russian, Ukrainian, Belarusian, German, French, Italian, Spanish, Portuguese, Turkish, Arabic, Korean, Japanese, Chinese, Czech, Danish, Greek, Estonian, Finnish, Lithuanian, Latvian, Norwegian, Polish — and roughly 100 more.

## Platforms & availability

- **iOS** (iPhone / iPad, iOS 16.4+) — App Store.
- **Android** — Google Play, direct APK, Huawei AppGallery, and RuStore.
- **Cross-platform core** — the app is being unified on Kotlin Multiplatform (KMP); the iOS app is rapidly catching up to Android (EPUB support, onboarding, profile screen, dark theme, dynamic swipe translation panel, custom AI actions, autotranslation), with more features now shipping to both platforms at once.

## Plans & pricing

Smart Book is free to download and read with. Two paid plans unlock AI and advanced features:

- **MAX (subscription)** — full access to all paid features for the paid period: AI actions and contextual AI translation, choice of text translator, offline downloading of paragraph translations, and auto-translation / auto-pronunciation for the narrator (Storyteller).
- **PRO (one-time payment)** — lifetime access to a fixed feature set. On its own, PRO doesn't include AI actions/contextual AI translation, translator choice, offline paragraph-translation downloads, or auto-translation for the narrator — but PRO users can add their own API keys, which brings PRO close to MAX in capability (you pay your own translation/AI costs).
- **Bring your own keys** — add API keys for popular services (e.g. Gemini, DeepSeek, Perplexity, Hugging Face, Chutes) or connect any provider via OpenRouter / any OpenAI-compatible service; available on any paid account.
- **Lighter one-time purchases** — separately remove ads or remove free-tier limits for a one-time payment cheaper than PRO.
- **Free tier** — free reading with some limits (e.g. on imported books, notes, and saved words), after which you make a payment or watch an ad. Android offers a free trial of paid features without entering payment details.
- **Payment methods** — Google Play, Stripe, and Binance.

## Download

- [Apple App Store (iOS)](https://apps.apple.com/us/app/smart-book/id1278697399)
- [Google Play (Android)](https://play.google.com/store/apps/details?id=com.kursx.smartbook)
- [Direct APK download](https://smart-book.net/apk/16)
- [Huawei AppGallery](https://appgallery.huawei.com/#/app/C107646007)
- [RuStore](https://apps.rustore.ru/app/com.kursx.smartbook)

## Site

- [Home](https://smart-book.net/) — overview, video, screenshots, description.
- [FAQ](https://smart-book.net/questions) — frequently asked questions with step-by-step answers.
- [Privacy Policy](https://smart-book.net/policy)

## How-to library (FAQ)

Step-by-step tutorials, each with a short video/post. Primary links point to the English Telegram channel; many are also mirrored on Reddit, YouTube Shorts, X, Instagram and TikTok.

### Translation
- [Translate text from other apps with Smart Book](https://t.me/kursx_en/44)
- [Show definitions instead of translations when tapping a word](https://t.me/kursx_en/173)
- [Compare translations from different services](https://t.me/kursx_en/32)
- [Enable offline translation for any part of the text](https://t.me/kursx_en/100)
- [Change the translation language while reading](https://t.me/kursx_en/114)
- [Auto-translate an entire chapter](https://t.me/kursx_en/143)
- [Reach the translator screen from different places](https://t.me/kursx_en/135)

### AI
- [Create your own AI prompt/action for a text](https://t.me/kursx_en/178)
- [See definition, etymology, examples & synonyms for a word](https://t.me/kursx_en/167)
- [Get a grammatical analysis of any text](https://t.me/kursx_en/132)
- [Use any AI for automatic translation](https://t.me/kursx_en/147)

### Dictionary
- [Save any word with a single click](https://t.me/kursx_en/180)
- [Add context to a saved word](https://t.me/kursx_en/11)
- [Export only certain words to a file](https://t.me/kursx_en/66)
- [Mark a word as learned and highlight it](https://t.me/kursx_en/93)

### Pronunciation
- [Fix pronunciation or voice problems](https://t.me/kursx_en/151)
- [Use AI voice for pronunciation](https://t.me/kursx_en/168)
- [Convert a chapter into an audio file](https://t.me/kursx_en/168)
- [Set custom pronunciation sequences](https://t.me/kursx_en/175)

### Books
- [Search within a book](https://t.me/kursx_en/137)
- [Copy the entire text of a chapter](https://t.me/kursx_en/112)
- [Start a book from the beginning](https://t.me/kursx_en/149)
- [Create a book from movie/video subtitles](https://t.me/kursx_en/162)

### Settings
- [Enable Bionic Reading mode](https://t.me/kursx_en/105)
- [Add your own font](https://t.me/kursx_en/54)
- [Adjust screen brightness with a swipe while reading](https://t.me/kursx_en/188)

### Other
- [Export or import learned words](https://t.me/kursx_en/113)
- [Get free access to paid features](https://t.me/kursx_en/144)
- [See all occurrences of a word in a book](https://t.me/kursx_en/171)
- [Add a shortcut to the current book on your home screen](https://www.reddit.com/r/KursX/comments/1d7pnm7/bookmarks_on_the_home_page)

## Articles & write-ups

- [Habr — reading foreign books with ChatGPT-powered context translation (RU, 2023)](https://habr.com/ru/articles/734790/): the origin story and how AI context translation was added.
- [Habr — AI-powered language-learning reader: engines, custom prompts, A1 simplification (RU)](https://habr.com/ru/articles/987932/): the current AI/translation stack (ChatGPT, Gemini, Claude, DeepSeek, DeepL, Google, Microsoft, Reverso, Lara, Yandex; Hugging Face / OpenRouter / Chutes) and features.

## Community & social

- [Telegram (English)](https://t.me/kursx_en) — feature tutorials and updates.
- [Telegram (Russian)](https://t.me/kursx)
- [Reddit r/KursX](https://www.reddit.com/r/KursX/) — announcements and how-tos.
- [Facebook](https://www.facebook.com/kursxapps)
- [X / Twitter](https://x.com/_kursx_)

Tutorials are also mirrored on YouTube (Shorts), Instagram (Reels) and TikTok.

## Developer & contact

- Developer: Stanislau Kurs (KursX) — [kursx.net](https://kursx.net/?utm_source=smart-book.net)
- Email: [apps.kursx@gmail.com](mailto:apps.kursx@gmail.com)
- Android package: `com.kursx.smartbook`
- iOS App Store id: `1278697399`