# Mars Book vs X

The clearest difference is in-app purchases: Mars Book at none against X's 10. Mars Book also leads on iOS requirement (9.0 vs 15.6). X's advantage is update cadence (every 3 months vs every 13 months). On price, ads and device support there is nothing between them.

Both are free to download. X sells 10 one-off in-app purchases. Mars Book asks for nothing beyond the download.

Mars Book ships an update every 13 months, X every 3 months. The most recent releases landed on October 13, 2026 and October 24, 2026 respectively.

## The numbers

| Metric | Mars Book | X |
| --- | --- | --- |
| Price | Free | Free |
| Rating | — | **[1.3 (3 ratings)](https://appshunter.io/ios/app/x-trails-pro/id1622662470/reviews)** |
| Number of ratings | — | **3** |
| Positive reviews | — | 0.0% of reviews |
| In-app purchases | **No** | Yes |
| Ads | No | No |
| Update frequency | Every 13 months | **Every 3 months** |
| Monetization | — | Free |
| Size | 14 MB | 46 MB |
| Requires iOS | **9.0** | 15.6 |
| Devices | **iPhone, iPad, iPod** | iPhone, iPod |
| Age rating | 4+ | 4+ |
| Developer | [Vixen Co.,Ltd.](https://appshunter.io/developer/536188843) | [Roni Waserman](https://appshunter.io/developer/1384422367) |

## What reviewers say

### Mars Book

[App page](https://appshunter.io/ios/app/mars-book/id1342509724)

**In-app purchases:** none


### X

[App page](https://appshunter.io/ios/app/x-trails-pro/id1622662470)

Explore the solar system, Earth's atmosphere, and its structure with engaging audio and video content. This app offers an entertaining and educational journey for all ages, created by a team of experts.

**Highlights:** Audio guides for Solar System Trail, On-demand content, Audio and video on Earth's atmosphere, Content on Earth's structure, Solar System exploration, Expert-created content

**Features:** macOS Compatibility

**In-app purchases (10)**

| Purchase | Price | Billing |
| --- | --- | --- |
| A Comet's Journey | $0.99 | one-time |
| Journey To The Centre Of Earth | $0.99 | one-time |
| A Mission To Mars | $0.99 | one-time |
| A Mission To The ISS | $0.99 | one-time |
| A Voyage To Saturn | $0.99 | one-time |
| Solar System Experience | $0.99 | one-time |
| The World Under Our Feet | $0.99 | one-time |
| Tour The Atmosphere | $0.99 | one-time |
| When Dinosaurs Moved | $0.99 | one-time |
| Moons Of The Solar System | $0.99 | one-time |


## Frequently asked questions

### Is Mars Book free?

Mars Book is free to download, with no in-app purchases.

### Is X free?

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

### Do Mars Book or X have ads?

Neither Mars Book nor X shows ads.

### Which is updated more often, Mars Book or X?

Mars Book ships an update every 13 months, and X every 3 months. Most recently, Mars Book was updated on October 13, 2026 and X on October 24, 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.*