That great news ! :D
Let me know if you encounter any difficulty coming from the way I implemented the OPDS feed.
I tried to stick to the specifications as closely as possible but I found some parts quite ambiguous.

Could you take a look at your log file and check if you have some errors ?

For now I'm quite puzzled by this problem. So if you have time to "play" a little bit with the settings (try to share another folder, create another user etc.) and find some hints, it would help a lot.

Ubooquity never modifies the user's files (books or comics). That's a strong design principle that will not change.
So modifying comics metadata is not an option.

However, keeping the unred/read state of a given book in the database (as well as the current page number for comics read using the online reader) is something that can be done (and already requested a few times).
So why not.

I understand your pain. ;)

I'll try to add a setting bypass the base folder when there is only one.

Perhaps you have a firewall on the computer running Ubooquity (Windows has one by default).

On my setup I had to open/forward ports on the DSL modem, the router, and the Windows firewall.

What makes you think the "Thumbs.db" file is the source of the problem ?

I'm asking because some RAR files are not correctly processed by the library Ubooquity uses to decompress them. Decompressing and recompressing them usually solves the problem. So the fact that your comics work after removing the "thumbs.db" file might just result from the recompression step, not the file removal.