[GH-ISSUE #1148] E999 error when send epub to Kindle #1708

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GiteaMirror · 2026-04-11T08:03:57-05:00

GiteaMirror commented

2026-04-11 08:03:57 -05:00

Originally created by @s3rg3ysh on GitHub (Jan 28, 2026).
Original GitHub issue: https://github.com/harvard-edge/cs249r_book/issues/1148

I'm getting E999 error when trying to sent epub file to my Kindle via Amazon's Send to Kindle page

Originally created by @s3rg3ysh on GitHub (Jan 28, 2026). Original GitHub issue: https://github.com/harvard-edge/cs249r_book/issues/1148 I'm getting E999 error when trying to sent epub file to my Kindle via Amazon's Send to Kindle page <img width="900" height="700" alt="Image" src="https://github.com/user-attachments/assets/469ba7da-b3be-4f03-80f1-3e3a4a65b16d" />

GiteaMirror added the type: bug area: book labels 2026-04-11 08:03:57 -05:00

GiteaMirror commented

2026-04-11 08:03:59 -05:00

@kent-williams commented on GitHub (Jan 28, 2026):

I just tried and experienced the same thing

@kent-williams commented on GitHub (Jan 28, 2026): I just tried and experienced the same thing <img width="767" height="638" alt="Image" src="https://github.com/user-attachments/assets/2af9d12b-d423-49ea-a381-2a3d8a8445a9" />

GiteaMirror commented

2026-04-11 08:03:59 -05:00

@profvjreddi commented on GitHub (Jan 28, 2026):

Thanks @kent-williams and @s3rg3ysh for reporting!

Quick question — is this the first time you're trying to send it to Kindle, or has it worked for you before?

I myself just use PDF, so honestly, the EPUB isn't something I have thoroughly debugged or made perfect. But I know it works on other readers for sure. I just haven't heard anyone mention Kindle before.

@profvjreddi commented on GitHub (Jan 28, 2026): Thanks @kent-williams and @s3rg3ysh for reporting! Quick question — is this the first time you're trying to send it to Kindle, or has it worked for you before? I myself just use PDF, so honestly, the EPUB isn't something I have thoroughly debugged or made perfect. But I know it works on other readers for sure. I just haven't heard anyone mention Kindle before.

GiteaMirror commented

2026-04-11 08:04:00 -05:00

@s3rg3ysh commented on GitHub (Jan 28, 2026):

It's first time to me, and this is only epub file (latest version) for this book I tried to upload via Send to Kindle page. I experienced the same error with other books as well, this for example https://github.com/victordibia/designing-multiagent-systems/issues/8. Unfortunately I cannot upload epub to my Kindle directly via USB, that only works for mobi files. Thanks

@s3rg3ysh commented on GitHub (Jan 28, 2026): It's first time to me, and this is only epub file (latest version) for this book I tried to upload via Send to Kindle page. I experienced the same error with other books as well, this for example https://github.com/victordibia/designing-multiagent-systems/issues/8. Unfortunately I cannot upload epub to my Kindle directly via USB, that only works for mobi files. Thanks

GiteaMirror commented

2026-04-11 08:04:01 -05:00

@profvjreddi commented on GitHub (Jan 28, 2026):

Ah, interesting — so it's not specific to our book. If you're hitting E999 on multiple EPUBs, you might have an older Kindle model? I should really get a Kindle, maybe I can get my kid one and tell her it's to debug our book 😅

Use Calibre (free) to convert the EPUB to MOBI yourself — would that work? When I get a chance I will try to play around with the Kindle side, but it's the start of the semester so things are hectic here :) Appreciate your patience!

@profvjreddi commented on GitHub (Jan 28, 2026): Ah, interesting — so it's not specific to our book. If you're hitting E999 on multiple EPUBs, you might have an older Kindle model? I should really get a Kindle, maybe I can get my kid one and tell her it's to debug our book 😅 Use [Calibre](https://calibre-ebook.com) (free) to convert the EPUB to MOBI yourself — would that work? When I get a chance I will try to play around with the Kindle side, but it's the start of the semester so things are hectic here :) Appreciate your patience!

GiteaMirror commented

2026-04-11 08:04:02 -05:00

@bl00dny commented on GitHub (Jan 28, 2026):

Ah, interesting — so it's not specific to our book. If you're hitting E999 on multiple EPUBs, you might have an older Kindle model? I should really get a Kindle, maybe I can get my kid one and tell her it's to debug our book 😅

Use Calibre (free) to convert the EPUB to MOBI yourself — would that work? When I get a chance, I will try to play around with the Kindle side, but it's the start of the semester so things are hectic here :) Appreciate your patience!

I have latest Kindle Scribe device and about hundred other epub (even published in 2026) books which I have uploaded with no issues. It's still me (s3rg3ysh), just replied from another GH account

@bl00dny commented on GitHub (Jan 28, 2026): > Ah, interesting — so it's not specific to our book. If you're hitting E999 on multiple EPUBs, you might have an older Kindle model? I should really get a Kindle, maybe I can get my kid one and tell her it's to debug our book 😅 > > Use [Calibre](https://calibre-ebook.com) (free) to convert the EPUB to MOBI yourself — would that work? When I get a chance, I will try to play around with the Kindle side, but it's the start of the semester so things are hectic here :) Appreciate your patience! I have latest Kindle Scribe device and about hundred other epub (even published in 2026) books which I have uploaded with no issues. It's still me (s3rg3ysh), just replied from another GH account

GiteaMirror commented

2026-04-11 08:04:03 -05:00

@panth commented on GitHub (Feb 17, 2026):

I am also facing the same issue and yes other books are going in fine to my kindle. I like Kindle because doesnt play on the eyes and gives distraction free reading experience.. Lets see :-(

@panth commented on GitHub (Feb 17, 2026): I am also facing the same issue and yes other books are going in fine to my kindle. I like Kindle because doesnt play on the eyes and gives distraction free reading experience.. Lets see :-(

GiteaMirror commented

2026-04-11 08:04:04 -05:00

@profvjreddi commented on GitHub (Feb 17, 2026):

Another user has reported the same issue in #1174 (now closed as a duplicate), indicating that this is affecting multiple Kindle users.

I acknowledge that this is a real issue — the EPUB I generate is not passing Kindle's validation. Based on @bl00dny's feedback (regarding Kindle Scribe), it appears that other EPUBs work fine, so the problem lies with what I am rendering and not with the device. The root cause is likely that our Quarto-generated EPUB contains elements that stricter validators reject. I have to figure this out. We have already encountered this issue with ClearView in #1052, including double hyphens in XML comments, CSS variables, and other factors. Still sifting through this in the midst of all the semester craziness here :) Kindle's "Send to Kindle" service conducts its own validation and is rejecting the file as a result. So if folks know how I can test this that would be helpful. Or if someone can help that'd be even more awesome!

@profvjreddi commented on GitHub (Feb 17, 2026): Another user has reported the same issue in #1174 (now closed as a duplicate), indicating that this is affecting multiple Kindle users. I acknowledge that this is a real issue — the EPUB I generate is not passing Kindle's validation. Based on @bl00dny's feedback (regarding Kindle Scribe), it appears that other EPUBs work fine, so the problem lies with what I am rendering and not with the device. The root cause is likely that our Quarto-generated EPUB contains elements that stricter validators reject. I have to figure this out. We have already encountered this issue with ClearView in #1052, including double hyphens in XML comments, CSS variables, and other factors. Still sifting through this in the midst of all the semester craziness here :) Kindle's "Send to Kindle" service conducts its own validation and is rejecting the file as a result. So if folks know how I can test this that would be helpful. Or if someone can help that'd be even more awesome!

GiteaMirror commented

2026-04-11 08:04:05 -05:00

@s3rg3ysh commented on GitHub (Feb 24, 2026):

As option you can download Calibre E-Book Management, open epub in Calibre E-book Editor and use Check book tool by clicking on Bug icon or selecting Tools -> Check book. This will give you list of errors with explanation and link to place in a problem file. Every time you fix the problem re-run Book check that you can see more errors (if any). Hope that will help you to identify potential type of issues and address them in automated manner.

@s3rg3ysh commented on GitHub (Feb 24, 2026): As option you can download [Calibre E-Book Management](https://calibre-ebook.com), open epub in Calibre E-book Editor and use Check book tool by clicking on Bug icon or selecting Tools -> Check book. This will give you list of errors with explanation and link to place in a problem file. Every time you fix the problem re-run Book check that you can see more errors (if any). Hope that will help you to identify potential type of issues and address them in automated manner. <img width="1771" height="351" alt="Image" src="https://github.com/user-attachments/assets/1114bfee-9469-40a1-af82-6a76050294c8" />

GiteaMirror commented

2026-04-11 08:04:06 -05:00

@profvjreddi commented on GitHub (Feb 24, 2026):

Oh this is super helpful! Thanks a bunch @s3rg3ysh -- I've been deep in making some big edits and working on vol2 so will circle back to this soon.

@profvjreddi commented on GitHub (Feb 24, 2026): Oh this is super helpful! Thanks a bunch @s3rg3ysh -- I've been deep in making some big edits and working on vol2 so will circle back to this soon.

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Reference: github-starred/cs249r_book#1708