[sricochet]

Send to Kindle has a timeout of 45 minutes. So if the book is large, has many images, or has many pages, it might timeout if it takes longer than 45 minutes to transfer to the library. I think that internet connection has nothing to do with it because the books are already uploaded to Amazon, it's a matter of the speed at which the book is transferred from the Amazon server to the Amazon content library

I have uploaded files from Delphi Classics that are quite large, and have much text but fewer pages and many images using techniques discussed above and elsewhere (convert EPUB to AZW3 to EPUB, reconstructing or completely deleting the Table of Contents), so I think the Delphi Classics formatting is pretty good.

I have tried to upload some texts from Digitale Bibliothek, with many images or pages, and they have failed, no matter what I did.

Then I tried splitting the files into smaller chunks with EpubSplit calibre plugin, and the split epubs uploaded after EpubCheck, checking for errors in calibre Edit Book option, and converting EPUB to AZW3 to EPUB in calibre and limiting TOC entries to less than 500, after deleting the Table Of Contents and creating table of contents with the Create TOC From Files.

It is very frustrating that Amazon promises a 200 MB upload limit on Send to Kindle Web and has such limitations that they are not advising on. It would be helpful if they publish the limitations somewhere and wouldn't waste people's time discovering these limitations.

However the 200 MB limit is very convenient and is a great feature for large epubs and I hope that Amazon keeps this limit or perhaps even expands it in the future, as there are many authors who are prolific and will perhaps publish large collections in the future.

Just a few observations for anyone who has run into this issue before or currently or in the future.