# duoBooks vs PSV. Operational Deck CES Test

The clearest difference is price: duoBooks at Free against PSV. Operational Deck CES Test's $5.99. duoBooks also leads on update cadence (every 2 weeks vs every 39 months). PSV. Operational Deck CES Test's advantage is in-app purchases (none vs 11). On ads, device support and iOS requirement there is nothing between them.

duoBooks is free to download; PSV. Operational Deck CES Test costs $5.99 up front. duoBooks sells 11 in-app purchases, starting at $2.99 per month. PSV. Operational Deck CES Test asks for nothing beyond the download.

duoBooks ships an update every 2 weeks, PSV. Operational Deck CES Test every 39 months. The most recent releases landed on October 13, 2026 and October 2, 2026 respectively.

## The numbers

| Metric | duoBooks | PSV. Operational Deck CES Test |
| --- | --- | --- |
| Price | **Free** | $5.99 |
| Rating | **[4.7 (55 ratings)](https://appshunter.io/ios/app/duobooks-language-learning/id1538452253/reviews)** | — |
| Number of ratings | **55** | — |
| Positive reviews | 68.4% of reviews | — |
| In-app purchases | Yes | **No** |
| Ads | No | No |
| Update frequency | **Every 2 weeks** | Every 39 months |
| Monetization | Free with in-app purchases | — |
| Size | 53 MB | 45 MB |
| Requires iOS | **15.0** | 15.6 |
| Devices | iPhone, iPad, iPod | iPhone, iPad, iPod |
| Age rating | 12+ | 4+ |
| Developer | [PlainProg LLC](https://appshunter.io/developer/1538452255) | [Maxim Lukyanenko](https://appshunter.io/developer/1496252741) |

## What reviewers say

### duoBooks

[App page](https://appshunter.io/ios/app/duobooks-language-learning/id1538452253)

Read any book in any language with instant translation and detailed word explanations. Build your vocabulary with a personal dictionary and spaced repetition tools. Improve pronunciation with audio voiceovers and master new languages through immersive bilingual reading.

**Highlights:** Instant translation of any book, Personalized vocabulary dictionary, Spaced repetition for memorization, Audio voiceovers for pronunciation, Bilingual parallel text reading, EPUB reader for custom files

**Features:** macOS Compatibility, Vision Pro support

**In-app purchases (11)**

| Purchase | Price | Billing |
| --- | --- | --- |
| Full Plan | $2.99 | per month |
| Full Plan | $6.99 | per month |
| Full Plan | $17.99 | per year |
| 6 Month Full Plan | $19.99 | per 6 months |
| Full Yearly Plan | $29.99 | per year |
| War and Peace | $0.99 | one-time |
| Silver Blaze | $0.99 | one-time |
| On The River | $0.99 | one-time |
| Clochette | $0.99 | one-time |
| The Fishing Hole | $0.99 | one-time |
| Alice in Wonderland | $0.99 | one-time |


### PSV. Operational Deck CES Test

[App page](https://appshunter.io/ios/app/psv-operational-deck-ces-test/id6455428592)

**Features:** macOS Compatibility

**In-app purchases:** none


## Frequently asked questions

### Is duoBooks free?

duoBooks is free to download, with in-app purchases available.

### Is PSV. Operational Deck CES Test free?

PSV. Operational Deck CES Test costs $5.99, with no in-app purchases.

### Do duoBooks or PSV. Operational Deck CES Test have ads?

Neither duoBooks nor PSV. Operational Deck CES Test shows ads.

### Which is updated more often, duoBooks or PSV. Operational Deck CES Test?

duoBooks ships an update every 2 weeks, and PSV. Operational Deck CES Test every 39 months. Most recently, duoBooks was updated on October 13, 2026 and PSV. Operational Deck CES Test on October 2, 2026.

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*Compared by [AppsHunter](https://appshunter.io/) from daily US App Store data. Review summaries are generated from verbatim App Store reviews.*