[stefan230]

Good morning,

I have a general question on how calibre works. I am trying to get to the root of a bug.

The general story is the following:
I have an E-book from Thalia (a german retailer for books and E-Books) and when I import the book into calibre it does something to the book. And I am trying to understand why and what it actually does to the book.

When imported my manga gets slighty changed by calibre which in turn leads to displaying problems on my Pocketbook E-Reader (Pocketbook Inkpad Color 3 (PB743K3)) in its PB-Reader software.

The working theory is that the E-Book I got from Thalia is either real EPUB2 or EPUB3. It is listed as an EPUB3 in its file though. I think that while importing calibre sees this and then corrects the file to be "proper" EPUB3. Which in turn makes the PB-Reader break. The Epub3 capabilities of the software are generally bad.

So generally I don't see this as being a bug with calibre but with pocketbooks PB-Reader and its lackluster Epub3 implementation.

I would like to report this bug to pocketbook later. In order to this I would like to understand *what* calibre exactly does to the book and *why* it does that. Is my working theory correct here at all? Is there some sort of Epub-sanitation? Is this something I could turn off?

I know this is not a problem with calibre, but rather the PB-Reader, since the same file works well enough with KOReader (But I still have other problems with that one, which are not related to this query).

I attached two content.opf files to this post. The original one from the E-Book from Thalia and a second one of calibre after importing the E-Book into it. I will also attach a diff screenshot from vscode aswell.

It would be nice if some could chime in and explain what happens here. I could boil my problem down to the first two lines of the content.opf which gets changed. So are these the lines which differentiate the unproper EPUB3 file from the proper one in calibre?