What Is BookKraft AI and Why We Built It
Good books fail for bad reasons. Not because the writing is weak — because the file is wrong, the metadata is missing, or the cover dimensions are off by a pixel. That’s why we built BookKraft AI: a set of ebook formatting tools for indie authors who’d rather write than debug EPUBs.
Here’s what it does, how we built it, and why.
The Problem We Kept Seeing
Most ebook publishing problems aren’t about the writing. They’re about the file. Authors hit a wall of technical requirements after finishing a manuscript: EPUB structure, OPF manifests, table of contents formatting, metadata standards, image size limits, CSS compatibility across devices.
None of that has anything to do with writing a good book. But getting it wrong means KDP rejections, Apple Books rejections, broken formatting on some devices, or a reading experience that undermines the work itself.
The pattern repeats. An author converts their manuscript to EPUB using Word, Calibre, or an online tool, then uploads to KDP. It goes through — KDP silently ignores structural errors during its conversion process. Then they try the same file on Apple Books or Kobo and get a rejection with a vague error message.
Back to square one. No clear explanation of what broke or how to fix it.
The tools to prevent this existed: EPUBCheck is a free validator, Sigil is a free editor. But using them required learning a technical toolchain that most authors didn’t want to invest time in.
What BookKraft AI Is
BookKraft AI is a set of sixteen web-based tools, each one handling a specific ebook publishing job. They run in your browser — no install, no signup required. For the free tools, your files never leave your device. Processing happens entirely in your browser using JavaScript.
The tools fall into three categories:
Validation and quality checking:
- EPUB Validator — runs the same structural checks that KDP, Apple Books, and Kobo use, giving you a prioritized error report before you upload anywhere
- Word Cleanup Checker — scans your manuscript for the formatting problems that become EPUB errors during conversion
- Cover Checker — verifies your cover image meets every platform’s pixel dimension, aspect ratio, and file size requirements
- Book Score — AI-powered analysis of your book’s overall publishing readiness, from manuscript quality to metadata completeness
Formatting and conversion:
- Full Manuscript Mode — converts your .docx or .txt to a valid EPUB 3.0 file with chapter detection and clean HTML in one step
- EPUB Formatter — fixes common EPUB formatting errors in an existing file without requiring a full rebuild
- TOC Generator — builds a properly structured EPUB table of contents from your chapter headings
- Kindle Format Fixer — corrects encoding, punctuation, and CSS issues specific to Kindle formatting
Content and metadata:
- Metadata Builder — generates correctly formatted metadata for KDP, Apple Books, IngramSpark, and Draft2Digital from a single form
- KDP Keyword Finder — uses AI to identify the seven search keywords most likely to help readers find your book on Amazon
- Blurb Writer — generates compelling back-cover copy from your manuscript summary and genre
The Design Decisions Behind It
Three decisions at the start shaped everything.
Free tools for the basics. EPUB validation, metadata building, cover checking, word cleanup, and manuscript conversion are all free — no account required. These are the tools every author needs, and there’s no good reason to put them behind a paywall. The free tools aren’t crippled demos; they’re the same quality as the paid ones. We make money on AI-powered features that require inference costs, not on validation that runs entirely in your browser.
One-time pricing, not subscriptions. You don’t need to pay monthly to publish a book. The AI-powered tools are available through a one-time Starter or Pro plan — pay once, use them as long as you need. No subscription that stops working if you take six months off between books. No tier inflation where features you need get locked behind higher plans over time.
No learning curve for the core workflow. Every tool has a clear input and a clear output. Upload your file, run the tool, get your result. Error messages use plain language: “your OPF manifest references a file that doesn’t exist,” not “OPF-032: manifest item not found.” The interface is simple because the underlying problems are already complex enough.
How Each Tool Fits the Publishing Workflow
The tools work in sequence — a publishing pipeline from raw manuscript to ready-to-upload file:
- Word Cleanup Checker → catches manuscript formatting problems before conversion
- Manuscript Mode → converts clean manuscript to valid EPUB 3.0
- Metadata Builder → generates correct metadata for all platforms simultaneously
- EPUB Validator → confirms the EPUB passes every platform’s structural requirements
- Cover Checker → verifies the cover meets every platform’s image specs
- KDP Keyword Finder + Blurb Writer → optimizes discoverability metadata before listing
You can enter at any stage. Already have an EPUB? Start with the validator. Already have good metadata? Start with the Cover Checker. Each tool works on its own, but they’re most useful end to end.
Who BookKraft AI Is Built For
BookKraft AI is built for indie authors who self-publish, for editors and book formatters working with multiple clients, and for authors in hybrid publishing arrangements who handle their own technical work.
It’s not built for large publishing houses — those have dedicated ebook production workflows and don’t need browser-based tools. It’s not built for developers who need API access to ebook processing. The target user is someone who writes books and wants publishing tools that work without becoming a technical expert.
What’s Coming Next
A few gaps we’re working to fill:
- Better print-to-digital conversion for books that exist only as PDFs
- Series metadata management for authors with backlists of 10+ books
- Deeper WCAG accessibility compliance checking for markets that require it
- Audiobook metadata tools for authors moving into audio distribution
If you have a specific ebook publishing problem that should have a tool but doesn’t, reach out via the contact page. Most of the current tools exist because someone asked.
Pro Tips for Getting the Most From BookKraft AI
- Start with the EPUB Validator on any existing file. If you have published books that were never professionally validated, run them through. You may find errors that explain formatting complaints in reviews or poor display on certain devices.
- Use the Word Cleanup Checker on every manuscript before conversion. Five minutes of cleanup saves 30 minutes of EPUB error fixing later. The step is easy to skip and almost always worth doing.
- Save your validation reports. Before making any fixes to an EPUB, save the full validator report. If you introduce a new error while fixing an existing one, the saved report tells you what was there before versus what’s new.
Once your ebook is formatted and published, your author photo is the next thing readers see. If you need a professional headshot for your KDP author page or book back cover, our AI Author Headshot tool generates 10 publish-ready headshots from a single selfie — no photographer, no studio — starting from $5.
Frequently Asked Questions
Is BookKraft AI affiliated with Amazon, Apple, or any publishing platform?
No. BookKraft AI is independent. We don’t have commercial relationships with KDP, Apple Books, Kobo, or any other publishing platform. The tools are built to help you publish successfully on all of them — we have no incentive to favor one platform over another.
Does BookKraft AI use AI for all its tools?
No. The five free tools — EPUB Validator, Metadata Builder, Cover Checker, Word Cleanup Checker, and Manuscript Mode — use in-browser processing without AI. They run as JavaScript in your browser, which is why your files never leave your device when using them. The AI-powered tools (Kindle Format Fixer, EPUB Formatter, KDP Keyword Finder, Blurb Writer, and Book Score) use Claude AI for the parts that benefit from language understanding and contextual analysis.
Can I use BookKraft AI for books in languages other than English?
Most tools are language-agnostic — the EPUB Validator, Metadata Builder, Cover Checker, and Manuscript Mode work correctly with any language. The AI-powered tools work best in English currently, with improving quality in Spanish, French, German, and Portuguese. For languages with right-to-left text (Arabic, Hebrew), the EPUB structural tools work but you’ll need to add dir="rtl" attributes manually to your EPUB content after conversion.
Is my manuscript safe when I use these tools?
The free tools process files entirely in your browser — nothing is transmitted to our servers. For AI-powered tools, your text is sent to our AI provider (Anthropic) for processing and is not stored after your session ends. We don’t use uploaded content to train models. Our complete privacy policy is at bookkraftai.com/privacy.
How does BookKraft AI compare to hiring a professional book formatter?
A professional book formatter brings design expertise, experience with complex layout scenarios, and accountability for the final product. BookKraft AI automates the technical compliance layer — making sure the EPUB is structurally valid, the metadata is correct, and the file passes platform validation. For authors who want design-focused formatting (custom fonts, chapter headers, decorative elements), a professional formatter and BookKraft AI complement each other: the formatter handles design, the validator confirms the output meets technical requirements before submission.