I am no longer maintaining the database of fanfiction for e-readers. Over the last several years, a couple of very smart folks have managed to create tools that will automatically download fics in the appropriate format for your e-reader (mobi for Kindle and epub for Nook).
My favorite tool is FLAG (Fanfiction Lightweight Automated Grabber), available at https://www.flagfic.com.
The instructions are pretty straightforward, and with a very few exceptions, hasn’t had any issues is pulling from fanfiction.net.
FLAGfic has been in a state of re-design for the past few years. From what I can tell, they’re re-developing it to be a browser plugin.
There’s a solid plugin for Calibre e-Book reader that handles fanfic downloads. https://calibre-ebook.com/