[davidfor]

Originally Posted by vietchovui

I have the same problem.

Um, no you don't. The OP is sideloading books via the USB cable using calibre as the mechanism to manage that. The books should be seen by the device when it is connected. For some reason they are not. You are using a third-party tool on the device to download books over WiFi. Not the same thing at all.

I can successfully send books to koreader on kobo via calibre wireless server. But after being disconnected from the PC, Kobo (nickel) cannot show newly added books. I just want to use koreader to add books, and use nickel to read because the default file structure view of koreader is too hard to find the book I want, especially when there are so many books on my device.

This is all working as designed. Kobo only looks for sideloaded books when after being connected to the USB port and ejecting the device. The only other times it looks is when you use the browser to download the books or when you sign into the Kobo account. There is a hack to trigger the search for new books, but, I have never needed to look at it. It is discussed in the Kobo forum.

And another problem is that the titles of old books in unicode UTF8 cannot display correctly. I've tried to restart the device but in vain. Any help would be appreciated. I have to overwrite unicode supported fonts to \fonts folder again to fix the font problem (but not the missing books in the library). Thank you

I think you are doing what you need to do. If the characters in the title are not supported by the system supplied fonts, need to sideload an appropriate font that will display them. Or change the title in the metadata for the books so that it is not needed. Whether that can be done probably depends on the language of the title.