ValueError: Not a ZIP file

[gianni_fed]

No, Divingduck,
I've no idea to what appened.
What I know is that I found many books corrupted in my Calibre library so, I have formatted the system disk and I have reinstalled windows 10 64bit and only the programs I use abitually.
I checked the health of my HD's that is perfect and without bad sectors.
I do not think so, but the fact that they are all SSD can mean something?
Bye,
Gianni

[Divingduck]

A lot of systems are using SSD's these day's w/o any serious problems.
calibre can't damage ebook files during an export/import all calibre data via the library maintenance menu. It simply don't modify any file during this process, it only takes care that all library and setup files will be part of a complete copy.

[gianni_fed]

Hello,
I'm sorry to have started this discussion but I was in a panic when I lost everyone here books.
I think I understood what caused this problem, even if I did not understand why it occurred.
Since my Caliber library contains about 30,000 volumes, I wanted to create many libraries, one for each literary genre, so I downloaded (save on disk) the books divided by genre on another disk.
Since I had to correct many books, I found that this was not the best way to proceed, so I reimported all the books, I had put on another disk, to Caliber and, to my surprise, the 1041 volumes lost are all Mystery novels, then there must have been a problem in one of the two operations (save on disk) or (Add books).
I hope that my accident can help someone not to make the same mistake.
Hello and thanks,
Gianni

[Divingduck]

Good to know what had happen with your library. Hope you will find the missing books somewhere in your backups.

An alternative of splitting libraries are virtual libraries. Maybe something you can think about. https://manual.calibre-ebook.com/virtual_libraries.html

[gianni_fed]

Originally Posted by Divingduck

Reading the complete thread and I'am still confused what you are doing...

a) You did a backup of your calibre library.
b) You are showing a program that tries to open a ZIP file and report a major error with opening an EPUB file.
c) You are telling that you loose +1k books by backing up the calibre database.
d) You are showing a report telling that the file you like to open isn't a valid EPUB file (calibre and Sigil).
e) And you are telling that the RAR is better than ZIP. Well, this is a more philosophic statement what have nothing to do with your fileor backup problem. In this case it is simply a book format decision and not a calibre owned decision (especially for the problem you have for now). Calibre needs only to deal with existing book formats and have no influence on format definitions.

But you don't tell exactly what you are doing. Nothing from what you wrote have to do with backup / restore so fare. There is a "not in fractional parts" story to tell. How should anyone give you a good support without knowing what exactly you are doing? By the way, it is common to tell also what calibre version and OS is involved in a problem.

The big question is, how exactly did you make the backup and how did you restore.

The error you are asking for tells you exactly what had happen if calibre tries to open the file. Your EPUB isn't a EPUB. This means either you have a corrupt file, format wise a corrupt zip archive or a non EPUB file with a wrong file extension. Calibre can't do anything with this file because of these specific information:

a) "BadZipfile: Bad magic number for file header"
b) "ValueError: Not a ZIP file"
c) Sigil shows you exactly the same problem
d) Your archive program too tells you there are major problems with the file.

This all is nothing that indicate calibre as a root cause so fare.
When something like this happen you will face out immediately tons of postings here as this is a elementary problem then.

You or your system obviously did something outside calibre with your files (in case you hadn't problems before to open this files within calibre). Any idea?

Best regards, DD

Hello to all.
as you can see from the attached file, I continue to have the "Not a ZIP file" error when I try to extract some books from my Calibre library with "Save on the disk" and "Save on the disk in a single folder".
What I don't understand is: why in all files the errors are exatly in the same lines?
Thanks.
Best regards,
Gianni

[ilovejedd]

Originally Posted by gianni_fed

as you can see from the attached file, I continue to have the "Not a ZIP file" error when I try to extract some books from my Calibre library with "Save on the disk" and "Save on the disk in a single folder".

That's the line number in the Calibre source code where it's hitting the error Hence, if the error type is the same on all your books, then the reported lines are going to be the same. Useful for debugging purposes to identify where the problem is.

In your case, most likely it's just the EPUB files themselves that are corrupted. Testing the EPUB files with WinRAR, WinZIP or 7zip, etc would confirm if your EPUB files are corrupted.

[anesthezea]

I get the same error message from the free epubs I get from the TOR book club every month.

[DNSB]

Originally Posted by anesthezea

I get the same error message from the free epubs I get from the TOR book club every month.

What operating system is on the device used to download the free epub?

[anesthezea]

Originally Posted by DNSB

What operating system is on the device used to download the free epub?

I'm using a Mac with macOS Mojave. I did email TOR books after posting here and figured out what the problem was in my particular case. When I clicked to download the ebook files, it was saving the download page instead of the book file. It would save the page as an epub or mobi file with the book title as the filename. I think the books that were giving me error messages were ones I had downloaded on my phone and saved to my dropbox. I redownloaded the latest TOR book from their website to my computer and it worked properly then.