Bookends vs CrackX
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
Bookends
Manage your research references and PDFs on your mobile device. Search online databases, import metadata, annotate PDFs, and organize your library. Offers basic functionality for free with optional one-time purchase and yearly subscription for advanced features like cloud sync and unlimited imports.
- Search online reference databases
- Import metadata and PDFs
- PDF annotation and markup
- Barcode scanning for references
- Cloud sync across devices
- Share online libraries
- Create multiple libraries
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Bookends is the reference management app you've been looking for. The basic version offers: • Search online sites directly (arXiv, Google Books, Google Scholar, JSTOR, the Library of Congress, PubMed, PubMed Central, and Semantic Scholar) or use the built-in browser (EZProxy-compliant) to download reference metadata and PDFs (access privileges required). Searches can return a maximum of 20 references, and only 50 references can be stored in your personal database. • Use unique identifiers such as DOI, PMID, ISBN, or arXiv id to autofill references. • View the text of PDF annotations in a note stream, and create your own with our powerful PDF markup engine. • Barcode scanning, one per day. • And many more features designed to help you discover, organize, and use reference information. Standard, one-time purchase ($14.99): • No limit on searches or importing. Premium, yearly subscription ($14.99). Requires a Standard purchase. • Cloud sync with all your iOS devices and Bookends for Mac (separate purchase). • Share online libraries with colleagues. • Scan documents with Mellel Mobile*. • Create multiple libraries. • Unlimited barcode scanning. • Extract PDF annotations with deep links to annotations and text. • Convenient UI to add PDF notes to the library. • Automate your actions with Shortcuts. * iPad-only. Requires a Mellel Mobile Premium subscription. Subscription is for one year and has an auto-renew option. The subscription can be managed in iOS -> Settings > [your name] > Subscriptions. A subscription will renew if it isn't canceled at least 24 hours before the renewal date. If the subscription is not renewed, Premium will be disabled but Standard will continue to work. Terms of Service: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/
CrackX
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Optimization of a Mixed-Feed Steam Cracker App is an interactive engineering tool for evaluating steam cracking performance and CO₂ storage feasibility. The app allows users to configure operating scenarios, compare key performance indicators, estimate process outputs, and assess whether captured CO₂ can be safely stored in a geological reservoir. It includes performance metrics, feasibility results, visual charts, and report generation to support academic analysis and technical decision-making. Designed for chemical and petroleum engineering education, the app helps connect process optimization with carbon management in one workflow.
Screenshots
Verdict
The clearest difference is in-app purchases: CrackX at none against Bookends's 2. CrackX also leads on iOS requirement (14.0 vs 18.6). On price, ads and device support there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
Both are free to download. Bookends sells 2 in-app purchases, starting at $14.99 per year. CrackX asks for nothing beyond the download.
| Parameter | Bookends | CrackX |
|---|---|---|
| Price | Free | Free |
| Rating | 4.7 (400 ratings) — better | — |
| Positive reviews | 76.4% of reviews | — |
| Number of ratings | 400 — better | — |
| Update frequency | Every 2 months | — |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free with in-app purchases | — |
| Devices | iPhone, iPad | iPhone, iPod |
| Requires iOS | 18.6 | 14.0 — better |
| Further details — not scored | ||
| Size | 114 MB | 26 MB |
| Age rating | 4+ | 4+ |
| Developer | Sonny Software, LLC | Fatima Bazroun |
Bugs and requests
Bookends
Reported bugs
3 issues- Incompatibility with iCloud Optimized Storage
- Unreliable sync between desktop and mobile versions
- Occasional data loss or corruption
Requested features
4 requests- Nested folders and tags for better organization
- Automatic PDF metadata extraction
- Improved search and filtering capabilities
- Seamless integration with third-party services
CrackX
Not enough reviews yet to summarise bugs or requests.
In-app purchases
Bookends
- Premium3 Months trial$14.991 Year
- Standard$14.99
CrackX
No in-app purchases









